Cant set cookie domain

Hey EE Community!

Experiencing a few odd problems on our msm sites - if we set a Cookie Domain under ‘Cookie Settings’ it goes blank on save - if we change Website Session Type under ‘Security and Session Preferences’ it goes back to what was previously set on save

note the Cookie Prefix will save but not the Domain.. most odd.

Anybody else have a clue what might be going on here? I’m sure it’s something simple I’ve overlooked but can’t seem to track down.

Thanks! J.R.