While performing an operation, Sharegate displays the following message:
SharePoint is not responding to connection requests from Sharegate at this time. Sharegate will attempt to reestablish the connection in 1 minute.
Any error ending with -289
This message is displayed when Sharegate receives too many network errors while trying to send requests to SharePoint. This could happen if the network or the SharePoint server are either down or too busy. The result is that Sharegate pauses the operation for a moment and then retries at a later time. It will start by waiting 1 minute and, if it keeps failing, it will gradually increase the wait time to a maximum of 1 hour (it will retry every hour until it succeeds or until canceled by the user). At any moment, you can force it to retry now by clicking on Retry.
Getting this message is a sign that there are problems either with the SharePoint server or the network. The best thing to do would be to contact your network or SharePoint administrator to see if those problems can be resolved so that Sharegate stops receiving connection failure errors.
If the problem is that the server or the network cannot handle the number of requests being sent by Sharegate, it can help to lower the performance level. This will lower the maximum number of requests that Sharegate can send simultaneously, which will help the network and the server handle them without giving errors.