Would appreciate to hear from other Coinomi users with similar experience.
Exactly the same happened with Coinomi ERC wallet about 11 months ago. They were stuck on block 377823 then. I contacted their support, notified them of the issue, they thanked me and said they will re-sync their wallet. It took then few days to fix the wallet if I remember correctly...
Interesting enough, though I use Coinomi for a number of other coins too, such issue happened with ERC wallet only. Some of other coins had connection issues at different times, but only ERC wallet was ever stuck on a block. But I wouldn't give that much importance, it is not necessarily connected to an issue with ERC; it can be an issue with their server resources or whatever else.