Maybe because you're trying to zap from the same WoS that you're receiving in? 

I've always been annoyed that Amethyst won't let you copy someone's lightning address.

I know you can do off Nostr zaps in Amethyst but I'd rather do them off Nostr completely.  

 No, it does not even generate the invoice. That happens before I vhose which wallet to use for payment. 

 It takes hitting the zap button & same amount 3 times before an invoice is generated. 

Yours isn't the only profile that seems to suffer from what looks like a timeout requesting a LN invoice. 

 For me it times out no matter how many times I try. I also cannot zap you. I will try upgrading my Amethyst a bit later.