Globally disabling the assessment system needs to be confirmed in System Settings.

Follow the order exactly:

1. Open up System Settings
2. In System Settings, navigate to "Privacy & Security". Leave Window Open in the Background
3. Open up Terminal (as separate window). DO NOT CLOSE System Settings
4. In Terminal, run "sudo spctl --master-disable" --> Type Password --> Click Enter
5. In System Settings, navigate out of "Privacy & Security" Page (For Example -- Click on "Lockscreen"), then navigate back to "Privacy & Security"
6. In System Settings --> Privacy & Security Page --> Scroll Down to bottom --> Select "Allow Application From" --> Select "Anywhere" (the option will now appear) --> Type Password
7. Completed

o_pasha wrote:

Globally disabling the assessment system needs to be confirmed in System Settings

Please do not attempt to do that. It is an extremely bad idea.

I did everything described in the post MacOS Sequoia -- "Allow Apps from Anywher… - Apple Community to install apps from anywhere

Another extremely bad idea. Those "honey pot" threads are like little capsules of internet-based misinformation here in the forums. The moderators have realized that it's better to keep these cancers in one place instead of allowing them to spread throughout the community.

I still can't install the app(

Follow instructions here: Safely open apps on your Mac - Apple Support

i even tried to disable SIP via safe reboot

When it comes to bad and dangerous ideas, you're on a roll here. If you haven't already, please turn SIP back on.

this is an app from my employer that all my colleagues have installed and without which I cannot work.

and there is definitely nothing wrong with it.

While I won't dispute that this is an app from your employer, there is most definitely something wrong with it. Your employer did not take the basic steps required to make the app installable. That costs $99. What does it mean for you when your employer either refuses to spend $99 and/or doesn't see the point in properly building software?

You do not need to disable Gatekeeper. Please follow the instructions in the link above. Specifically, look for the section titled: If you want to open an app that hasn’t been notarized or is from an unidentified developer

If your employer supplies the app then you need to ask them how to install it on your system. Why aren't they helping you?

Well, so no one is, and if they do they may have the same result. Personally I've never seen the message you posted on my Macs running Sequoia not could I find it doing an online search. Without the app it's not possible to test it. Perhaps someone will have an idea.

Personally, I would not attempt to install whatever app that is.

Are all your colleagues running Sequoia?

Hello, did you by any chance manage to fix it? I'm losing my mind.