Macbook Pro: Problem getting external HDD to recognize

Is the drive being connected directly to the laptop? Try connecting the drive to the other USB-C port. Also try rotating the USB-C connector 180 degrees upside down to see if that works better. I know this sounds crazy, but it can make a difference if the USB-C port(s) are half bad. I've personally experienced this on the USB-C Macs I've repaired that had damaged USB-C ports.

Is the laptop's charger connected directly to the laptop as well? Connecting the charger to a multi-port adapter, dock, or hub may not allow all of the charger's power to reach the laptop.

I've never heard of that brand adapter before so I have no idea how compatible and reliable it is.

FYI, this laptop may be eligible for multiple free Apple repair programs. The most important ones are for the SSD and Battery so definitely check out these two programs:

https://support.apple.com/13-inch-macbook-pro-solid-state-drive-service

https://support.apple.com/13inch-macbookpro-battery-replacement

Here is the current list of the publicly acknowledged free repair programs for various Apple products (some products like this laptop have multiple programs available):

https://support.apple.com/service-programs

The user should always maintain at least 20GB of free storage space on the macOS boot drive for the normal operation of macOS. In fact if they want to upgrade the OS, they will need to have at least 35GB+ of free storage to upgrade to Big Sur. Plus running out of free space on an APFS volume may prevent the APFS volume from being able to be mounted to access the data or to delete files to make room due to how the APFS file system works.

Also inform the user to always have frequent and regular backups. It is impossible to recover accidentally deleted data from an SSD after the Trash has been emptied plus an SSD can fail at any time without any warning signs. This is why I highly recommend checking to see if the laptop qualifies for the free SSD repair program. I've seen the SSDs on these 2016-2017 non-Touchbar models have a higher rate of failure than most other Macs even when the laptop doesn't qualify for the free SSD repair program. Plus as far as I'm aware there are no USB adapters for connecting this proprietary Apple SSD to another Mac to recover the data in the event the laptop doesn't power on.

SyComputing wrote:

Update: HWTech solved the issue.

"Also try rotating the USB-C connector 180 degrees upside down to see if that works better."

This indicates your USB-C port is most likely half bad. Unfortunately with the non-Touchbar model this would require a Logic Board replacement even if the issue was due to bad contacts on the USB-C port since the I/O Ports are soldered to the Logic Board. There is a slim chance there is something stuck to some of the pins on the USB-C port, but it can be difficult to impossible to clean the connector without removing the Logic Board from the laptop. It is nearly impossible to even get a visual on the contacts of the port connector. I've missed seeing some liquid damage and even burn marks on those pins until I removed the Logic Board.

SyComputing wrote:

I'm assuming here by "Logic Board" you mean in Windows parlance, "motherboard"?

Yes.

If that's the case, using your links for the recall, I've confirmed the machine is eligible for HDD repair. But is it even worthwhile to have the customer send the unit in for repair with the mainboard problem looming over him? It sounds like this is an engineering defect that might present other issues going forward.

The free SSD repair program involves Apple running an app to confirm if the SSD has a problem and to attempt to update the SSD's firmware if necessary. If this doesn't succeed, then Apple will replace the SSD for free. From what I've personally experienced with various SSDs over the years I highly recommend to have Apple check out the SSD. I do know that I've had to replace several of our organization's SSDs in these 2016-2017 non-Touchbar models because the SSD's have failed (they did not qualify for the free repair program). I think these particular SSDs have some quality issues. In theory Apple should address the SSD issue as long as nothing else interferes with the process. Having an Apple Store or AASP which actually performs the work themselves is best as they are more likely to overlook any other issues with the laptop since an Apple mail-in repair depot may refuse to perform a partial repair if other issues exist (some stores or AASPs do mail the laptop to Apple).