Seems like BP Share and Clans Reborn still having issues. Real hit and miss with BP sharing, players have complained that players when leaving and rejoining aren't getting BP's shared with them again.

So losing blueprints when leaving a clan works fine but when joining after leaving players don't always get shared blueprints back to them?

yes, that appears to be the issue in this particular case. What they said was...
When a new clan player was invited to the clan a message popped up about blueprints being shared, BP's seemed to work. The player was removed from the clan, then brought back in ... and BP sharing seemed to stop working, the player has zero shared BP's and any BP's he earns don't get shared the other way either, but that could just be becuase they may already have the BP's I don't know.

I found whilst testing that the the share blueprints on join feature wasn't working at all whilst using Clans Reborn. I have now fixed this issue in the latest update for the plugin.

Thank you, I will apply the fix now.