AG group stuck at Synchronizing

Hi

I have a SQL 2014 cluster with 2 nodes, I have an availability group with 6 databases. Nothing is happening in the databases but they are still showing as "synchronizing" on the Secondary node.

I have taken them out of AG and started again but it still will not sync so that I can fail over.

There is another Instance with another AG on the same servers running and that is working fine.

Please can someone help?

Thanks

Sam