I can view recordings online by not on my phone?
Since you do have them on the web page start with removing the app and reinstall it. You can also try rebooting the phone in between. Also make sure you don't have any filters selected in the library on the app.
It was a remporary issue with my phone. I just rebooted it and I could view recordings. I asked in the r/arlo section too. Only 4K recorded clips were not visible though.