Site claims third-party cookies blocked but Enhanced Protection is disabled - how to fix?

I have problems with multiple sites that claim that third-party cookies are blocked and do not work even though though the Enhanced Tracking Protection is disabled for the site (the shield icon is grey and striked-through). In particular it is teams.microsoft.com and Instapaper (their saving bookmarklet sends me always to a site reading "enable unrestricted third-party cookie access for www.instapaper.com" - though this might be a different issue than Teams). I have read https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop?redirectslug=enable-and-disable-cookies-website-preferences&redirectlocale=en-US#w_how-to-tell-when-firefox-is-protecting-you and https://support.mozilla.org/en-US/kb/websites-say-cookies-are-blocked-unblock-them (trying even to "forget" the teams website; not doing the full wipe out of everything). How to troubleshoot / fix this? I am a technical person so I can dig into it if just somebody points me in the right direction... Thank you!