Adding reason and solution to an error message in the TroubleShooting section

[kittybest]

Prerequisites

Please answer the following question for yourself before submitting a feature request.

• I checked to make sure that this request has not already been filed

Motivation

So far, there's only one error mentioned in the troubleshooting section: https://maci.pse.dev/docs/troubleshooting
The error message displayed on console only points out the low level reason, instead of the high level reason, which causing user not knowing what exactly they could do to solve that problem.

Details

Listed out blocks of error messages in comments with the reason and the solution to it.

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