There's a guide for fixing this issue with the Chrome extension, but the guide instructs the user to disable blocking of third-party cookies.
The problem is that this is a global setting. It won't affect only ClickUp, but ALL websites and extensions.
This solution weakens security and privacy protections and most users won't even realize that. It has the potential to expose users to hacks and undesired marketing (through retargeting, for example), and to leak private information. I'm not a lawyer, but it's even conceivable that this advice could make ClickUp liable for inadvertent violations of GDPR and other modern privacy laws.
It's not a coincidence that this setting is disabled by default by increasingly popular privacy-aware browsers such as Brave.
Other extensions that do some of the things that ClickUp does seem to manage without creating this unnecessary exposure, and it would be great if ClickUp could find a better solution as well. Until then, the extension is effectively broken.