Could not load file or assembly Sage.Peachtree.Domain

SOLVED

Hi

I have written a windows service that speaks to Sage 50. It runs on three computers. On only one computer, I see this in the logs:

2020-07-09 11:01:27.277 -04:00 [DBG] Could not load file or assembly 'Sage.Peachtree.Domain, Version=2020.2.0.219, Culture=neutral, PublicKeyToken=d06c16dde04d83e4' or one of its dependencies. The system cannot find the file specified.
System.IO.FileNotFoundException: Could not load file or assembly 'Sage.Peachtree.Domain, Version=2020.2.0.219, Culture=neutral, PublicKeyToken=d06c16dde04d83e4' or one of its dependencies. The system cannot find the file specified.
File name: 'Sage.Peachtree.Domain, Version=2020.2.0.219, Culture=neutral, PublicKeyToken=d06c16dde04d83e4'
   at Sage.Peachtree.API.PeachtreeSession.Begin(String applicationIdentifier)
   at IWErpnextPoll.ErpnextService.OpenSession(String appKeyID)

Consequently, the said computer never gets to connected to Sage. What could be the cause of this?