This is most likely due to the size of the input file. Each platform has different restrictions on file size and response timeouts. For example, Microsoft Power Platform imposes a strict 2 minute timeout on all responses via a connector whereas Azure Frontdoor allows a more generous 4 minute max response time. Based on extensive testing against the various infrastructure components our development team has identified an upper bound of 10MB uncompressed (.wav) and 1MB compressed (.mp3, .m4a, .ogg, etc.) for input audio files in a flow or app. This is under ideal conditions, using backend components all in the same Azure region so mileage may vary depending on your Power Platform tenant location.
Salesforce also imposes restrictions on the amount of information transmitted and received, although it seems to be less uniform. Sometimes, a 1MB compressed audio file will work, other times it will fail. It is important to note that Salesforce imposes limits on the size of files that can be transmitted and stored via Apex code. This may vary by org so check with your administrator to determine what the limitations are for your environment.