1. As an initial troubleshooting step, regenerate preferences using "restoredefaultpath" and "rehash toolboxcache". Refer to the following MATLAB Answers post for more information:
Move to step 2 if this does not resolve the issue.
2. Does the following command run from the Command Window with proxy server enabled? This step is to check if MATLAB's Web preferences are not routing through the System Web Browser.
>> web("https://www.mathworks.com/help/releases/R2020a/matlab/ref/plot.html");
If the above command runs without error, move to Step 3. If the command throws an error, there is a possibility that the proxy server is not connected. The proxy server can be configured and tested by following the steps in the below MATLAB Answers post:
3. Change the help browser renderer by following the below MATLAB Answers post and observe if this resolve the issue:
4. If none the above steps help, check to see if a fresh install of MATLAB R2020a with proxy enabled resolves the issue.
5. As a last resort, download the attachment 'matlabwindowjava.jar' and use it to replace the existing JAR file present in the following location, where <matlabroot> refers to the location MATLAB R2020a is installed:
<matlabroot>\java\jar\toolbox\matlab
MATLAB needs to be restarted after replacing the JAR file with the attachment.
