Loudspeaker issue

I have Adobe Connect on my Android smart phone (Galaxy Note 5). I haver similar issue when I use a newere smart phone (A51) as well.

When I am listening to a presentation, it works fine until someone calls me on my phone number. I reject the call to continue with listening. But, afterwards, the loudspeaker turns off and I could not figure out how to turn it on again. Has anyone had a similar issue? I have Googled the issue and gone through the Connect forum, but could not find any solution.