Im not well versed in this but when I palyed with btc pay, did you create a payment received message (idk could do something), I was paying through a node so did see I wouldnt get notifications unless used BOS on telegram, could be keysends since was having issues with emojis on the node, last is you can always use alby and connect your node and push through there ln address (its technically counting on alby but it has consistently pushed notifications if forwarded through). Sorry haha just all stuff i played with but not as technical as you.