Keep in mind GMB is a Google product and this requires a Gmail to access/manage.

In the dashboard do you see if you get a ‘duplicate’ business error message?

If they’ve completely disappeared from your dashboard then it could mean you’ve lost access to them.

User levels
– Primary Owner
– Owner
– Manager
– Communication

If you aren’t a primary owner then other owners can remove your access.

If someone has tried to claim your business, there’s a certain time period where Google attempts to contact the Gmail associated with the GMB (so check your Gmail inbox for any indicator of this).

The GMBs industry is pretty ruthless because of how valuable they are to local businesses so you need to make sure you are monitoring them at least monthly if not more given your specific industry.

Otherwise, Google could have merged the 3 GMB’s into 1 because they don’t like having several GMBs for 1 website if there’s no legitimate reason to have it. Best to check with Google’s My Business policies to see if your set up violates it.