user4012: Incurred an error starting /plutus-apps client and connecting to localhost: user error, Interpreter Error, CompilationErrors
Short Error
  plutus-playground-server: user error (Error evaluating simulation: 
  InterpreterError (CompilationErrors [CompilationError {filename =

Computer:

macOS Monterey (v12.1)
Macbook Pro 2015 Intel Quad Core i7

Steps:

Started nix-shell in plutus-playground-server, and successfully ran plutus-playground-server
In new terminal tab, ~/plutus-apps, nix-shell successfully ran
Updated dependancies sudo GC_DONT_GC=1 npm install -g npm
start client cd plutus-playground-client and npm run start (Error occurred here)

Full Error:
  plutus-playground-server: user error (Error evaluating simulation: 
  InterpreterError (CompilationErrors [CompilationError {filename = 
  "\n/private/tmp/web-ghc-work-16cc79e7d9a477a7/Main.hs", row = 2, column = 
  1, text = [" error:","    Could not find module 
  \8216Playground.Contract\8217","    Use -v (or `:set -v` in ghci) to see a 
  list of the files searched for.","  |","2 | import Playground.Contract","  
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^"]},CompilationError {filename = 
  "/private/tmp/web-ghc-work-16cc79e7d9a477a7/Main.hs", row = 3, column = 1, 
  text = [" error:","    Could not find module \8216Plutus.Contract\8217","    
  Use -v (or `:set -v` in ghci) to see a list of the files searched for.","  
 |","3 | import Plutus.Contract","  | 
 ^^^^^^^^^^^^^^^^^^^^^^"]},CompilationError {filename = "/private/tmp/web- 
 ghc-work-16cc79e7d9a477a7/Main.hs", row = 4, column = 1, text = [" error:","    
 Could not find module \8216PlutusTx.Prelude\8217","    Use -v (or `:set -v` 
 in ghci) to see a list of the files searched for.","  |","4 | import 
 PlutusTx.Prelude","  | ^^^^^^^^^^^^^^^^^^^^^^^"]}]))

References

Unable to start /plutus-apps client application


user4012: When starting the client server on macOS use GC_DONT_GC=1 npm run start.
That is, include GC_DONT_GC=1 in front of the command npm run start.
Then, open a browser tab to http://localhost:8009/ and, using Brave Browser, Advance from warnings. (Not https, see note below).
Note: I had to update my Plutus-apps/plutus-playground-client/webpack.config.js file per prodineeritecht's recommendation to bi-pass the https proxy firewall.

4012: <p>Incurred an error starting /plutus-apps client and connecting to localhost: <strong>user error, Interpreter Error, CompilationErrors</strong></p>
<p><strong>Short Error</strong></p>
<pre><code>  plutus-playground-server: user error (Error evaluating simulation: 
  InterpreterError (CompilationErrors [CompilationError {filename =
</code></pre>
<p><strong>Computer:</strong></p>
<ul>
<li>macOS Monterey (v12.1)</li>
<li>Macbook Pro 2015 Intel Quad Core i7</li>
</ul>
<p><strong>Steps:</strong></p>
<ul>
<li>Started <code>nix-shell</code> in plutus-playground-server, and successfully ran <code>plutus-playground-server</code></li>
<li>In new terminal tab, ~/plutus-apps, <code>nix-shell</code> successfully ran</li>
<li>Updated dependancies <code>sudo GC_DONT_GC=1 npm install -g npm</code></li>
<li>start client <code>cd plutus-playground-client</code> and <code>npm run start</code> (<strong>Error occurred here</strong>)</li>
</ul>
<p><strong>Full Error</strong>:</p>
<pre><code>  plutus-playground-server: user error (Error evaluating simulation: 
  InterpreterError (CompilationErrors [CompilationError {filename = 
  &quot;\n/private/tmp/web-ghc-work-16cc79e7d9a477a7/Main.hs&quot;, row = 2, column = 
  1, text = [&quot; error:&quot;,&quot;    Could not find module 
  \8216Playground.Contract\8217&quot;,&quot;    Use -v (or `:set -v` in ghci) to see a 
  list of the files searched for.&quot;,&quot;  |&quot;,&quot;2 | import Playground.Contract&quot;,&quot;  
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^&quot;]},CompilationError {filename = 
  &quot;/private/tmp/web-ghc-work-16cc79e7d9a477a7/Main.hs&quot;, row = 3, column = 1, 
  text = [&quot; error:&quot;,&quot;    Could not find module \8216Plutus.Contract\8217&quot;,&quot;    
  Use -v (or `:set -v` in ghci) to see a list of the files searched for.&quot;,&quot;  
 |&quot;,&quot;3 | import Plutus.Contract&quot;,&quot;  | 
 ^^^^^^^^^^^^^^^^^^^^^^&quot;]},CompilationError {filename = &quot;/private/tmp/web- 
 ghc-work-16cc79e7d9a477a7/Main.hs&quot;, row = 4, column = 1, text = [&quot; error:&quot;,&quot;    
 Could not find module \8216PlutusTx.Prelude\8217&quot;,&quot;    Use -v (or `:set -v` 
 in ghci) to see a list of the files searched for.&quot;,&quot;  |&quot;,&quot;4 | import 
 PlutusTx.Prelude&quot;,&quot;  | ^^^^^^^^^^^^^^^^^^^^^^^&quot;]}]))
</code></pre>
<p><strong>References</strong></p>
<ul>
<li><a href="https://cardano.stackexchange.com/questions/6320/unable-to-start-plutus-apps-client-application">Unable to start /plutus-apps client application</a></li>
</ul>
 4012: <p>When starting the client server on macOS use <code>GC_DONT_GC=1 npm run start</code>.</p>
<p>That is, include <code>GC_DONT_GC=1</code> in front of the command <code>npm run start</code>.</p>
<p>Then, open a browser tab to <code>http://localhost:8009/</code> and, using Brave Browser, Advance from warnings. (<em>Not</em> http<strong>s</strong>, see note below).</p>
<p>Note: I had to update my <code>Plutus-apps/plutus-playground-client/webpack.config.js</code> file per <a href="https://cardano.stackexchange.com/a/6329/4012">prodineeritecht's</a> recommendation to bi-pass the https proxy firewall.</p>
