I uploaded a map ("Editable Map") and was viewing it in Collector on a Microsoft Surface Pro. The next day, I tried accessing the map but I got a "failed to open" error. I uninstalled and reinstalled the program but still have the same error. I can open other maps, just not this particular one.
Are you the owner of the concerned webmap? If yes, then please check if the concerned webmap and its layers are working properly on browser (ArcGIS Online).
In case you are not the owner, then you need to check with the owner of the webmap if the map is working fine on browser, and the map is shared with concerned group/organization.