It is because you have the modalBehavior option set to “fail”. It needs to be “execute” or default. Just use {} for the batch play options and it will set them to default.
Say this louder for the people in the back! If you don’t pass in empty brackets, batchplay refuses to run at all, which is in direct opposition to the official documentation example.
incorrect example:
https://developer.adobe.com/photoshop/uxp/2022/ps_reference/media/photoshopaction/#batchplay
In addition, is there any way to see when a batchplay fails, or why it fails? There is no messaging in the UXP Dev Tool log, and combined with the sometimes-false official documentation, it requires pure-luck to figure out what is going on.