I have investigated your case.
1. Investigation:
1.1
First of all, I have noticed that the «Stripe» extension is not installed in your store despite I have installed it earlier:
1.2
I have tried to install it again using the official installation instruction
I have got a failure: «Authentication failed for code.dmitry-fedyuk.com».
Your store uses the login / password authentication for the Mage2.PRO code repository, but the credentials in the Composer’s auth.json file are wrong:
Solution:
Step 1
You should set the right credentials in the Composer’s auth.json file.
See also the «Authentication failed for code.dmitry-fedyuk.com» topic for more detailed explanation.
If you do not know your password for Mage2.PRO code repository, then you can restore it.
Step 2
Then you will be able to install the «Stripe» extension using the official installation instruction.