Unable to see my Sandisk external SSD anywhere.

Continued....

I hope someone is able to help me ASAP because I'm literally tweaking. I've tried EVERY possible solution I could find here and on YouTube but to no avail.

Are you running any anti-virus software, cleaning/optimizer apps, or third party security software? These types of apps are not needed on a Mac and usually causes more problems than they solve. If you have any of them installed, then uninstall them by following the developers' instructions.

If you are using any third party apps to manage the external drive, then make sure they are up to date and compatible with macOS 15 Sequoia. Some of those apps may not be compatible yet and may be weeks or longer before the developer updates their software to work with Sequoia (this is another reason upgrading the OS to a new major version so close to release is an issue).

Have you tried booting into Safe Mode to see if that makes any difference? If you are using a third party NTFS driver or the manufacturer's proprietary software, then this probably won't work.

Make sure to disconnect all other external devices in case one of them is causing a problem. And connect the drive directly to the Mac. Make sure to try each of the other USB-C ports especially on the other side of the laptop.

How much Free storage space do you have on this Mac (ignore the "Available" value since it is very misleading)? If you have at least 80GB+ of Free storage space, then you can create a new APFS volume (give it a unique name). Then install macOS onto this new APFS volume. However, do NOT install any third party software. Do NOT migrate or restore from a backup. Do NOT sign into you AppleID or iCloud. See if you can access the external drive under these conditions. If you can, then you should be able to access the files on the other macOS installation to transfer them to the external drive. It also confirms you have a software or configuration issue with the other OS installation.

If you choose this latter option for testing, then before deleting the new APFS volume, make sure you re-select the old original OS as the default startup volume in the Startup Disk System Settings in order to prevent any boot issues. Also, you could install your previous version of macOS instead of Sequoia, but you would need to create & use a bootable macOS USB installer:

Create a bootable installer for macOS - Apple Support

neuroanatomist wrote:

Open applications > utilities > disk utility. Does the SSD show up? Can you mount it?

That is a good idea, but incomplete. Since at least macOS 10.13, the physical drives are hidden by default in Disk Utility. With macOS 10.13+, a user needs to click "View" within Disk Utility and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility. Here is an Apple article showing the process:

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Destroy it with a brick, if it’s causing you this much stress.

More pragmatically, check the firmware revision as some Sandisk SSDs have known firmware issues.

https://support-en.wd.com/app/firmwareupdate

Also check with Sandisk support, as well.

quonniee wrote:

I've tried everything I could. Using different cables, rebooting my laptop and even updating it to MacOS Sequoia...

FYI, when you are trying to troubleshoot a problem, it is never a good idea to upgrade to a new major version of macOS because you will be introducing even more unknowns.....especially with a recently released OS which will always have unknown launch day bugs that may take a month before they are resolved. It is fine & a good idea to install the minor OS update patches since they will typically fix known issues with an existing OS & rarely introduces new problems. The only other time it could be Ok would be when it is 100% certain that the new major OS version is known to resolve that problem & no fix is being backported to the older OS.

The issue is most likely due to some third party software that has been installed, or a configuration issue, a compatibility issue with other devices, or an actual hardware issue.

I really need to transfer files to a disk and I don't have any other way of doing it because they're all on this laptop..

So does another drive have the same problem?

If you need these files elsewhere, some options can be using network file shares such as macOS File Sharing if sharing to another computer on your home network, or you can use some sort of cloud storage option depending on the situation and whether it is just for you or whether the files are intended for others. Of course if the files are of a very sensitive nature, then cloud based options may not an acceptable option.

I've been able to get this disc running on Windows, even formatting it to exFAT and FAT32. This disc also runs on an android phone I own and even on my mom's iPhone.

What file system is on this drive? And what system was used to partition & format this drive?

Are you using the manufacturer's proprietary software to manage this drive?

FYI, Apple rewrote the exFAT & FAT32 driver last year with the release of macOS 14.x Sonoma. This rewrite definitely seems to have introduced some problems for some users. Even with the older driver, many times people found macOS would have issues accessing such formatted drives when formatted with Windows since Windows may utilize other File Allocation sizes than are compatible with macOS, so usually it is best to use Disk Utility on macOS to erase the drive. Besides, other operating systems tend to be a bit more forgiving when any issues arise.

This is frustrating me because it asked me for permission for SOMETHING I don't even remember what but the disk definitely got recognized on this laptop at least ONCE. After I pressed allow, nothing else happened.

If you are using an M-series laptop, then there are security settings for the Thunderbolt ports. I personally have my settings configured to allow any USB/Thunderbolt device to connect to my M-series laptop when the laptop is unlocked. The default settings were to prompt every time a device was attached, but I found that sometimes those prompts would get lost behind another window. I would suggest changing these settings at least temporarily while you are troubleshooting this problem. Here is an Apple article:

If your Mac asks you to allow an accessory to connect - Apple Support

Allow accessories to connect to Mac - Apple Support

Open applications > utilities > disk utility. Does the SSD show up? Can you mount it?

See if your SanDisk SSD is one of the ones with the known firmware issues which I mentioned in this other post here:

SanDisk Extreme SSD firmware issue & data loss -- HWTech - Apple Community

quonniee wrote:

Update: Apparently this specific disk has this problem and is not officially recognized due to firmware issues or whatever...

I've just now come across a review that has literally this same exact problem!!! I'm tweaking out cuz this thing was 89.99$ !!!!

Fricking scammers

I had forgotten. I've been very happy with SanDisk memory cards (SD and CF/CFe) for photography, but they have a bad reputation for SSDs (and had it even before this more recent fiasco).

What about going to about this Mac top left hand corner under your apple pull down?