I want to clarify some things here, did you encounter any error message? If there's no error message received. You can try importing feed via private browser.
There are times that the browser is full of frequently accessed page resources, causing some unusual responses. We can start by accessing your account in a private browser. This mode doesn't save your searches, visited pages, log in details, and cookies.
Here's are the shortcut keys:
Ctrl + Shift + P (Internet Explorer or Firefox)
Command + Shift + N (Safari)
Ctrl+ Shift + N (Google Chrome)
Once signed in, let's try log on to QBSE and import again to double-check it.