I had the same problem with my Argus Pro and couldn't figure out how to delete recordings from the SD card. But after a bit of trial and error, I found a solution that worked for me.

What I did was use the Reolink app on my phone. I selected the camera I wanted to delete recordings from and went to the "Playback" tab. From there, I selected the date range for the recordings I wanted to delete and clicked on the "Delete" button. The app then asked me to confirm that I really wanted to delete the recordings, and after I clicked "Yes", it got rid of them for me.

One thing to keep in mind is that if you do delete recordings from the SD card, they're not necessarily gone forever. There are recovery tools you can use to get them back. So just be careful and make sure you really want to delete them before you go ahead and do it.