Sorry to hear you are having some trouble with the extension. As a troubleshooting step I would normally suggest deleting and re-installing it but can see that you have already done so.
One more thing I would do is log in through Shopify. Once logged into Shopify go to Apps > Oberlo and then try to import again. This has helped me in the past.
Otherwise I would suggest reaching out to our support team at firstname.lastname@example.org. They will be able to investigate with more details about your browsers and operating system. Hope this helps!