I had the same issue with not seeing my mounted drive when starting Cryptomator as admin (SyncBack can’t see the Cryptomator drive) and removing --options CURRENT_SESSION solved it.
Before this topic was linked to me by @infeo, thus fixing my problem, I also realized something. The reason why people can’t access the unlocked vaults via normal means - Windows Explorer is that explorer.exe is not running as admin. That’s also the reason why some copy etc. operations in the system drive show a UAC prompt.
For anyone who doesn’t want to remove --options CURRENT_SESSION and wants to run Cryptomator as admin, a simple workaround is to access the vault by running a third party file explorer as admin. Another thing I was contemplating before applying this fix was to make a task using Task Scheduler, to run Cryptomator as admin on startup instead of using the built-in option. This might be a good solution for those who don’t want all users to access the unlocked vault, but also don’t want to manually start Cryptomator as admin every time.