Each of your banking institutions may have different connection statuses, which you can find here.
It is possible that the status of an institution does not change automatically. For example, the status may remain as "error", while your account is well synchronized. To update it manually, you can change the tab in the application and then return to My Finances. This will refresh the page and the status will change.
If it still doesn't work, report an error for that institution. To do this, you can click on the Edit button and then the Report a problem button. Please do not remove this financial institution from your holdings until you are told to do so! Doing so will delete your data and we will lose track of the nature of the problem.