I’m mainly a Daedalus guy but I use Yoroi sometimes. For a few days now it has failed to sync some wallets.
It’s version 3.4.0 of the Chrome extension running in Brave browser on Win10. There are three wallets, all standard Shelley. Over the past several days one of them has synced occasionally, the other two not at all (actually says “Never synced”). Mostly I give it a few minutes then give up and close the tab, yesterday I left it for a while, didn’t help. Previously, I had no problems, was able to divide my holdings into different wallets for staking to different pools a week or so ago. Everything looks fine in Daedalus since I restored the new wallet created in Yoroi.