I just gave this a try on my side with a few surveys and haven't seen any issues so far. Are some of your surveys still opening? I would also be curious if you are able to open the ones that are giving you problems in the field or desktop app.
Please check to verify that the feature service is still present within the Survey folder of your ArcGIS Online Organization Content page. You can do this by clicking on the same 'globe' icon shown in the previous screenshot and select 'View item details in your ArcGIS Organization'.
It sounds like there may be a disconnection that happened with the survey and the feature service, leading to the error that you are seeing. If you downloaded the survey to your mobile device prior to the event, you would still be able to open the survey using the field app, but likely be unable to submit. You can try this as a test as well (attempt submittal of survey from field app)