I just gave this a try with a few different surveys and it seems to be working for me. A few ideas to narrow this down:
1. Does it do the same thing in multiple web browsers? (Chrome, IE, Firefox)
2. If you log into arcgis.com instead of survey123.arcgis.com, are you able to view your feature layers & add them to new maps without any problems?
Thanks for your response.
1. Yes, it is happening in 4 different browsers: Chrome, IE, Firefox, and Microsoft Edge.
2. Yes, if I log into arcgis.com I am able to view my feature layer and add it to maps.
Also, if you are loading over http, try loading over https. If you have not used the website since the last update, then also clear your browser cache (although given that this happens on all browsers it is unlikely the root cause).