I see lots of other folks running into this and thought I would post the fix along with my thoughts. (TL;DR).
The error message is “We can’t display this page because your browser blocks cross-domain cookies, but you can view this page in Salesforce Classic. Click here to open this page in Salesforce Classic.” It can happen in several screens and is a result of some of the base domain changes that Salesforce has been making coupled with the security changes browsers have been making. For chromium-based browsers (Edge, Chrome, Brave, etc.) the fix is to add your domain to the cookie exception list.
With screens, the process go as follows:
Click the Add button and
Note: You could use a wildcard in place of the sub-domain for all salesforce domains, but I don’t recommend that as it would leave you vulnerable to some miscreants that use their orgs for nefarious purposes.
- Go to Settings > Privacy and security
- Select Cookies and other site data
- Paste your sub-domain and domain path in the Site dialog
- Check Including third-party cookies on this site
- Click Add button
- Refresh your Salesforce screen [F5]
© Scott S. Nelson