Hi Naomi,
Why did you ask here and not in the Redgate forum ;-)
From my understanding, to have it working... you should update to the latest version of Redgate tools... for example, SQL Prompt had a last update 21st of February and one in January where it explicitly says that it supports SSMS 19... so maybe your Redgate Plugin is "too" old.
On the other hand... Redgate Tools are definitely supporting SSMS 19... so that should not be a problem.
I hope my answer is helpful to you,
Your
Bjoern Peters
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