Check your walletnotify and blocknotify lines in the config. The plugin recommends the correct config to you when connection is not possible.
The curl commands specified in these lines should be executable.
There are many reasons why the commands may not be executing. For example, maybe curl is not installed.
-s argument (silent) and the redirect to
/dev/null, and run a command from the shell to see if it hits the wallet api.
For example, if the plugin recommends that you add to your config:
walletnotify=curl -sk https://example.com/wallets/api3/notify/BTC/wallet/TXID >/dev/null
then login to your wallet server, and run the following command in the shell:
curl -k https://example.com/wallets/api3/notify/BTC/wallet/TXID
where TXID should be replaced with a TXID that you wish to notify for.
Let me know if you have any questions about this.