8 month regression and sleep training

Our 8-month old was sleeping well on his own in the crib. Cried for a couple minutes but would fall asleep on his own. Would make it until 7am. We did the Ferber method when sleep training.

The last two nights, he refuses to sleep on his own and when he wakes up, he refuses to go back to sleep. We tried everything including letting him cry almost to an hour with no stop in sight. We finally picked him up and he stopped but refused to stay asleep back in the crib. Not sure if it’s teething, a regression, growth spurts all hitting at once. But should we do the Ferber method again or break for a few days and try sleep training again?