Summary of issue:
I can't link to the portal despite having the key to it
Device: iPhone 7 Plus
OS: iOS 13.6
App Version (Settings > Scroll to the bottom): 2.51.1
known bug long ago . only that works for me is restart scanner ,, have android s10+ ...
I think it's old bug and new bug altogether. Before there were issues with linking only when you tried to link and get "error", for example 9th link from portal, so if it would happen to me I knew that i need to restart ingress. But after newest update it happens more frequently even without getting "errors" and then it's not clear when to restart.
something broke long ago, before u got message that u cant link if max outgoing links reached.... but when u dont get any error message why u cant throw link and it works after restart its very frustrating...