For 7.3 Version and higher and using IE 11?. 

1. Navigate to Sage CRM logon page,
2. Click on the Settings Icon on the top right corner
3. Click on Compatibility View Setting
4. Uncheck Display Intranet Sites in Compatibility View
5. Remove CRM server host name from the list.
6. Click Close.

See Knowledge Base 28595 for IE settings and Knowledge Base 79063 to clear the browser cache and cookies

Hi There, 

If you still have this issue then below is the workaround:

1. Open Sage CRM 2018 R1 (using HTTP) > Administration > System > System Behaviour 
2. Ensure "use browser session security" is disabled
3. Logout
4. Login using https link now you should not have this problem.

This has been escalated to L3 for a fix to my understanding.

Regards,

Ravi

Another workaround is to enable browser cookies or add the CRM URL's IP/Hostname in the browser cookies exceptions.

This issue is resolved in Sage CRM 2018 R2

I'm running 2018 R3 and got this issue using Chrome and a prompt about the dashboard not working. I switched to use IE and it seems fine.