Mirroring not working after a server crash
The likely issue is that the principal has had log backups performed since the mirroring session was paused and it cannot catch up, so re-initializing the mirror with a full and log backup should fix the problem.  First you will need to remove the mirroring from both servers with:

alter database [mydb] set partner off


Then restore the full and log backup with NORECOVERY and re-run through the mirroring wizard.