before and after installing the ceritificate I cannot save settings (no proxy)
Logs attached. Sorry for the delay. Your message went to junk folder for some reason.
It looks like that you have access to the AWS Cognito, but probably your corporate proxy is preventing access to the other required Fiddler API endpoints (like api.getfiddler.com). Could you please verify that you could access the required Fiddler endpoints listed in this documentation section?
In order to sign in successfully you'll need access to amazonaws.com and *.getfiddler.com. Without this access it is not possible to have a stable working product. Can you try opening https://dashboard.getfiddler.com and sign in there - this should help us to determine exactly which URLs are blocked on your side. If you are working behind some firewall, can you try to ensure the *.getfiddler.com addresses are accesible?