Hello @mskallerup,
Welcome to the Klaviyo Community!
Do you by chance have access to multiple Klaviyo accounts or multiple login credentials? If so, I believe the most likely cause is permissions related. I would ensure you are only logged into one Klaviyo account/Klaviyo credential at a time when working. Otherwise, if you switch into a different account/credential but have another tab open and then attempt to resume work in this other tab of the previous account, this sort of behavior can occur due to an authentication error of your credentials not matching.
I also assume this may be a localized issue as our Klaviyo sessions are typically not so short a timeframe that you would be logged out if you were actively working. To rule out any browser specific causes, I would advise trying to use either an incognito browser/private browser or some alternative browser. It’s oftentimes also a good idea to clear your cache and cookies and refreshing your browser.
Additionally, VPNs, certain browser extensions, and anti-viral softwares are known to cause odd behaviors when using Klaviyo due to their own setup on what they perceive as “suspicious” and block or not block.
I hope this helps!
David