Mobile Apps Signing Out

Our whole staff has recently started having issues with the phone app signing us out - we are a mix of iPhone and Android users and all have this issue.  An example of a common occurrence is that I'll get a notification that I have a new message in Zoom and need to sign in to see it.  When I try to sign in, I then get a message that I need to input a code from my desktop device to validate my phone.  The problem is that if I am usually not at my desk when this happens, and now I can't access Zoom.  How do we get our phone accounts to stay signed in at all times?