MP3 trouble

I just downloaded Audacity about 3 weeks ago. I use a PC with the latest Windows 10 software. When I get through with my recording, which sometimes uses up to 8 tracks, I merge it into one track and export the new track with everything included and save it as a MP3 track. When I send the MP3 file out to people via a text message to their phones Some people have iPhones and some android. Yesterday someone told me when they opened the file on their iPhone it would stop every 8-9 minutes and they would have to restart it. So they went to their office and played it on their Apple Computer. Same problem. Is the way I’m saving it to an MP3 file the problem. I would think not. I can play the file and my wife can play the file on our iPhones and iPads and MacBook Pro computer just fine. Any ideas on what would cause this?

How many people?

Just one person had a problem?

Here is some more clarity.

My wife and I have iPhones, too.

We just played the MP3 file I set up in audacity and sent out to a lot of people and when our screens went dark after two minutes the MP3 file quit playing. Just contacted Apple. They tell me this is an Audacity problem and I needed to get with Audacity to get something changed in settings so this will not happen. To them I’m using a third party app and they cannot fix it. Can some help me?

Do you mean that you exported some audio from Audacity as an MP3 file?

Why did your screens go dark?
Do you mean that your screen went dark after two minutes, or do you mean that the MP3 file quit playing to minutes after your screen went dark?
What app are you using to play the MP3 file?
I assume that you are referring to the screen on your iphone (?) How did you transfer the MP3 from your computer to your iphone?