Unity 2019.2.21 to 2021.1 error. Need help upgrading

It might be that under the new Unity you need to install a package for the old GUI system (like GUITexture)… that would be one place to check first. Here is some more reading:

Remember: NOBODY memorizes error codes. The error code is absolutely the least useful part of the error. It serves no purpose at all. Forget the error code. Put it out of your mind.

The important parts of an error message are:

  • the description of the error itself (google this; you are NEVER the first one!)
  • the file it occurred in (critical!)
  • the line number and character position (the two numbers in parentheses)

All of that information is in the actual error message and you must pay attention to it. Learn how to identify it instantly so you don’t have to stop your progress and fiddle around with the forum.

How to understand compiler and other errors and even fix them yourself: