When I go to build the source as per the instructions I get this error. IT says something about a missing dependency.

This is the error --> https://scans.gradle.com/s/dgerwa5aeqzq6

Versions: 1.16 github code

• Minecraft: 1.16.4
• Forge: forge:1.16.4-35.0.1_mapped_snapshot_20200916
• Mantle: Unknown
• Tinkers Construct: Unknwn

Can it be reproduced with just Tinkers Construct? If not, list the other mods required to reproduce the issue. Yes

Your issue looks like a common failed to connect to server gradle issue. Our build.gradle works fine when run from our build servers or dev enviroments, so I'm more inclined to blame the build site you are using. In any case, people without experience developing mods to be able to debug gradle issues really should not be building Tinkers from the source anyways. We will release an alpha when its ready.