I understand that it is not autofilling.

• Have there been any changes made in about:config?
• Also, do you have cookies enabled?

No, I haven't changed anything and I have cookies enabled, however I found autofilling working for mozzilla website.

You mentioned that it was also just the username. If there is a site that is not storing a password, you may need to give it permission or it may be blocking the storage of the password. There is an add on called Password manager that you can check to see if the site also store the password.

Since it is working for one site and not the others it may not be an application permission issue for the keyboard autoconfig.

I have the password saved,the problem is that I have to type the username manually then the password will be filled. On the other hand firefox for windows autofills both the username and password without typing anything.

Maybe the reason is that all my passwords are synced from pc and may not work on mobile version of websites