UiPath App stuck at Loading your app or showing: "There was an issue evaluating the expressions in the assembly"

News Knowledge Base
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in some scenarios the customer can face issues where an specific app is stuck stuck at "Loading your app" or be showing "There was an issue evaluating the expressions in the assembly" when trying to preview or after published.

Root Cause

This issue can have several root causes, but generally, the root cause will be related to a missing dependency, necessary for the app to work.

Resolution

To determine if there was an issue with some of the GET requests for the app, the following steps need to be followed.

  1. Collect a HAR trace while loading the app.
  2. In the HAR trace, look for failed response statuses. Several string keys can be used for finding the requests, but looking for the next string in single quotes 'status":' in the HAR trace to point to all the requests made to check one by one, look for statuses that are not successful (200). This can be done in any text editor, such as Notepad++.

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  1. If the status is 403, it means the request is not being authorized/being blocked from the customer's end, VPN providers or apps such as Zscaler can block the requests. It is worth having the client network team have a look into this.
  2. If 404 is shown, it could be an issue with the server where the dependency is stored or its accessibility, and UiPath needs to fix it.
  3. The URL the App is trying to access can be found scrolling up in the HAR from the status code.
  4. More information on the issue can be found by scrolling down after the failed status in the "text" tag, where more relevant details to resolve the issue can be found.

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  1. Other response codes may have different root causes that need to be investigated if they cannot be determined from the HAR trace. In this scenario, the HAR trace can be shared with support for further troubleshooting.