There are new betas of the Mac and iOS clients up. I have tried to address issues with synching between your own devices. If you see and error instead of the message on synching, send a few messages back and forth. If it doesnt work for you, I recommend readding your account in Monal. This will create a new device in OMEMO, so you will need everything you contact to trust the new device. This should generally happen automatically with most apps.