Device may have firewalls or browser cache issues, have you checked into this? I have had the same where both have prevented logins from retaining even after enabling the settings to allow "remember device" or retain login related settings. Another thing perhaps would be the shared settings on the survey itself. Is it organizational shared, private, or a public survey?
Hope this helps steer you towards an answer, I've had this problem a few times and am eager to hear if there are more than one resolution I can try whenever I encounter it again.
God bless,
Jansen Lyons - Records and GIS Section - Public Works - City of Rio Rancho, NM