So I am working on a Sitecore 10.1.2 project, and we’re using TDS 6.0.0.36. When I tried building the update package I got the error:

GENERATEPACKAGE : error : Could not find assembly sitecore.data.resourceitems.protobufnet.dll
GENERATEPACKAGE : error : Could not find assembly sitecore.data.resourceitems.abstractions.dll
C:\git\Blah\packages\HedgehogDevelopment.TDS.6.0.0.36\build\HedgehogDevelopment.TDS.targets(186,5): error : The package builder failed. Please set the build logging level to Normal or Detailed and see the build output log for more information on the failure.

This was odd, as Sitecore 10.1.2 does not contain either of those assemblies. But they did look familiar. After a bit of digging, I found them… in Sitecore 10.2. But I’m not using Sitecore 10.2… but that’s what it’s looking for.

To fix this I created a folder and dropped various required assemblies into it – including the 2 assemblies from Sitecore 10.2 – and then set the Sitecore Assembly Path setting (in the Update Package tab of the TDS project properties) to point to that folder.

EDIT: I raised this with Sitecore support. Their advice was to do what I’ve already done.