Login won't work on PC but does on mobile

I’m going nuts here. Please help.

Since this morning, I can no longer login on my https://www.domain/wp-admin

Regardless of user name/pass I enter and hit login, it just sits there and loads the mainpage. No dashboard. I could enter any bogus login/pass and there are no error messages.

I went through hours of solutions (disabling all wp plugins via my server cpanel), etc… nothing works.

This happens on all my 3 PC’s at home and all browsers. (yes, cached cleared, cleared cookies as well).

If I disable my laptop’s wifi and have it connect to my 4G mobile connection, I can suddenly authenticate on my wp-admin.php page.

My host says the issue is either my router or my ISP. I went through a router reset, updated firmware and re-configured wifi network. Same problem. I called my ISP and they say this is out of their realm of support.

Any clues what could be causing this?

Thanks!