I am using RapidWeaver 8.9.4 together with Stacks 5.1.2. I am getting an information of updated version Stacks 5.30. After update an error occurs when I load my website projekt “Missing plugins: Stack”. The only way to continue work is replacing Stacks 5.30 with the old version Stacks 5.12.
Why don’t you simply download version 5.3 of the Stacks plugin from the YourHead downloads page? 
I’ve seen this error before 
what version of macOS are you running?
Stacks 5.3 and up requires macOS 10.15 or newer — If you’re on an older version of macOS then you need to stay on Stacks 5.1.2
The webpage says Stacks requires “10.12 or newer” but this isn’t the case anymore. @isaiah or @joeworkman should probably get that page updated.
FYI: Older versions of Stacks can be downloaded from here.
Hi Dan, good advice - I work on Mojave (OS X 10.14) but can switch to another Mac with Catalina (10.15) or Monterey (12) Thank you !