Lit, Simple Lit and Complex Lit Shaders are not Avaiable

I am trying to change my Projects Render Pipeline to URP. I did install all the necessary packages and Upgraded all the Materials in my Project.

There are just a few numbers of problems. I can’t seem to change to the Lit, Simple Lit, or Complex Lit shaders, only the newly created materials are
Lit:

194287-screenshot-2022-03-22-152130.png

When I search for Lit Shaders, it shows up in the Categories as Failed to Compile/Universal Render Pipeline/Lit, and the same also goes for the Simple and Complex Lit shaders.

Secondly, my custom shaders are also just not working. They are either pink or are just Default Shader.

I also get this error code :

[Worker0] Shader error in 'Universal Render Pipeline/Simple Lit': Couldn't open include file 'Packages/com.unity.render-pipelines.universal/Shaders/SimpleLitInput.hlsl'. at line 136

with this warning message:

The package cache was invalidated and rebuilt because the following immutable asset(s) were unexpectedly altered

If anyone has an idea of why this is happing. All the suggestions are very appreciated.

_

Updated Unity from version 2020.3.30f1 to 2021.2.16f1. Everything seems to work alright now.