Additional questions I would be asking you are:
Do you have an ArcGIS Server? YES
Do you have an ArcGIS Server with rest services open to the public? YES
Did you setup token security on your ArcGIS Server? YES
Is the rest service secured? If "Yes". Did you add the rest services into AGOL from your ArcGIS Server? If "Yes". Did you save the user account and password to open the layer up in an AGOL web map. (So users do not need to log into ArcGIS Online and then log into the ArcGIS Server rest services to open up the secured data.) YE
Resurfacing this thread with similar issue on AGOL.
If I create a Web Mapping application from the Map Viewer with Simple Viewer template, when shared the user is redirected to login page:
https://uni-lj.maps.arcgis.com/apps/View/index.html?appid=5ae7930aae04460fb13bf16d6d720a31
Using the same Web Map and procedure but with Minimalist template, the user has no problem accessing the web app:
https://uni-lj.maps.arcgis.com/apps/Minimalist/index.html?appid=e07d276afe6a4bd081121e8c4b8bc976
The map itself can also be accessed:
Could there be a widget in the Simple Viewer causing the bug?
(I'm testing on Chrome in Incognito tabs)
I had the same issue in the Information Lookup template. The web app is embedded in our website as an iframe and there's also a hyperlink to it on the same page. The embedded iframe works with no problems, everything is shared publicly, no sign in required. When clicking the hyperlink, however, the app would open in another tab, and require a sign in. I opened the web map itself to test it and there were no issues opening it that way; something in the wep app template was forcing the sign in.
It finally worked after I went to configure the Information Lookup application we created and unchecked the 'Show the basemap selector' under Options. Now the hyperlink works on the website and does not require a sign in. When this option was checked, the basemap selector worked fine in the embedded iframe, but not with the hyperlink.
I hope this helps others.
This was precisely where I was stuck as well. Thank You! ... Thank You! ... Thank You!