Quick question about app not working

[AgentPidge]

Hi, I have a BT.com email account. I've had the app on my phone for ages. A few days ago unusually it said "Your session has timed out" and said to login again. When I try, it says it's not available at the moment and to try again later. I can get into my emails by searching for BT email online on the phone and also on the computer. So should I uninstall the app, and then install it again? Is there any risk that I'd lose anything?

The reason I'm hesitating is that I installed a banking app on my phone recently and after that couldn't login online like I used to. An agent said the app invalidates the online method. It doesn't sound like the same with the BT one, but is there another way rather than uninstalling, or is that the easiest way?
TIA

I would try uninstalling and re-installing the app. If the issue isn't resolved, please detail the name of the app, and your phone OS (i.e. iOS or Android)

Thank you. I uninstalled it and then reinstalled it. Unfortunately, they wanted to verify my identity by text, which is hopeless where I live (texts don't arrive) and so I tried email by Googling (as above) but I was logged out on that too! So couldn't verify by email or by text. So I'll try again tomorrow, somewhere where I can get texts.

>please detail the name of the app, and your phone OS