Transact-SQL:
To resume a suspended SQL Server database mirroring session using T-SQL, run this code from either database mirroring partner:
ALTER DATABASE [Database_Name] SET PARTNER RESUME
This will resume paused database mirroring and place the mirror database from SUSPENDED to the SYNCHRONIZING state (and finally in SYNCHRONIZED state if the safety level is FULL and the mirror catches up with the principal):
SQL Server Management Studio:
To resume a SUSPENDED SQL Server database mirroring session from SQL Server Management Studio:
Connect to the principal server instance -> Right-click the database -> select Tasks -> click Mirror:
Click ‘Resume’: