CalendarSync - CalDAV and more

purchased and got message that it couldn't be installed on some of my devices.

No support. I have written the author 4 times over the last 2 months after purchasing this app for $10.99, and not a word from them. I originally purchased this app in 2020 for my old phone and it worked great, so when I upgraded my phone I purchased a new license, I'm having issues setting it up, so I clicked "ask for support", outlines my problem and week after week no response. I'm moving on to a different app. I'll just write off the $10 bucks.