First hunch is a time-out.
The use of Invoke-WebRequest can be combined with a time-out. However, none is present and the default is 0 (indefinite) according to the PowerShell documentation at Invoke-WebRequest (Microsoft.PowerShell.Utility) - PowerShell | Microsoft Learn.
So a time-out is unlikely.
Alternatively, the Invantive App Online server can have closed the connection. Maximum runtime for a request on Invantive App Online and Invantive Bridge Online is 6 hours, but something may have a caused an earlier end.
The easiest to analyze this is to visit Invantive App Online Monitoring at https://app-online.cloud. It displays all requests of the last 8 hours. Find your request and click on it to view the details (more information on More insight with new Bridge Online Monitoring).
Is there an error code or exception listed in the details?
Do the individual steps at the end provide a hint?
Is it possible to (anonymized) include a full screenshot of the details in Invantive App Online Monitoring in your answer?