OVH client interface goes into a login loop on anything other than Chrome. There are a few sites like this which are the only reason I have Chrome installed.
I've been able to solve that on a few sites by turning off the "enhanced tracking protection" next to the address bar (haven't tried OVH specifically).
For OVH I tried a lot of things, disabling extensions (one by one, and all of them), using a blank (firefox) profile, the usual cache/cookie invalidation, disabling various privacy protection enhancements (one by one and all of them), etc. Chrome worked.
For other sites yes, often just cache/cookie invalidation is enough.