One way in which you can regain access is to reinstall the SQL Server and attach all databases to the new instance. This solution is time-consuming, and to recover the logons, it might require restoring the master database from a backup. If the backup of the master database is older, it might not have all information. If the backup of the master database is recent, it might have the same logons as the previous instance; so, administrators are still locked out.

Option 2: Complete the Microsoft procedure on how to connect to the SQL Server when System Administrators are locked out.
For details, see this Microsoft article to give the sysadmin role to a new administrator account.

To perform the steps above, you must be logged on to Windows as a member of the local administrators group and you must have SSMS already installed on the system.

After you perform the procedure, you can connect normally with the new account that's now a member of the sysadmin fixed server role. Then, browse and modify settings for the ePO database and related instance.