Problem with logging in via the app (internet connection from the cellular opetaror via wifi, all ok)

Hello
For several days I have not been able to log into the Cloud via the application (Android phone), when I use the Internet with my mobile operator, When I use WiFi everything is ok and I log in without any problems
I am asking for help and advice. I have already reinstalled the application, reset devices (cloud and router), unfortunately it did not help.

I would like to add that today I noticed that it is also impossible to log in to Cloud via www when I try to do it from the browser on the phone
Shows that the Cloud is offline, but it is not

@Danowa
What application are you talking about? What My Cloud device do you own? What version of firmware? When you say mobile operator are you talking about LTE, 5G etc.?

I have 2 My Cloud devices One Gen 1 and Gen 2. Both have up-to-date software. Connection problem with app occurs on both devices.
In the configuration of devices or routers (port forwarding, addressing etc.) I did not change anything all the time it was ok and it has not been working for a few days
My internet connection is LTE

I have the same setup and my problem is getting a good connection when I am away from home. My phone has 5G but most of the time I get LTE and, in some spots, I don’t get anything.

5G Definition (techterms.com)

LTE (Long Term Evolution) Definition (techterms.com)