If you are trying to load an MP3, the likely culprit is that it is a Variable Bit Rate (VBR) file. Converting it to a Constant Bit Rate (CBR) file almost always fixes the issue.
When encountering the error "Avidemux cannot use that file as audio track," it typically indicates that Avidemux is having trouble processing or is incompatible with the specific audio file you've tried to add to your project. This issue can arise due to several reasons, ranging from incompatible file formats to corrupted files. Let's break down the potential causes and solutions: avidemux cannot use that file as audio track