Why can I no longer sent invoices to my customers?

It could be that you're using a trial account, Ealasaid. You're only allowed to send up to 100 emails if you're using the trial version.

If this is what causing this behavior, you'll want to Subscribe so you can send unlimited emails. You can also share the invoice link instead. You can follow this steps on how to share it:

1. Create the invoice as usual.
2. Select the Save and share link instead of Save and send.
3. Click on Copy link.

Once done, you can now send it to your customer via email, SMS, other available messaging service. If you'd like, you can also send the invoice using the WhatsApp. 

If you haven't receive any error, here are the troubleshooting steps we can perform to help you send it. Let's start by using an incognito window. From there, try to send the invoice to see if it'll work. If yes, we just need to clear the cache. There are times when you'll encounter an unusual behavior if the browser saves too much cache.

Also, let's try to use a different browser. This helps to determine if the browser you're currently using has issues. I'd suggest accessing your account through Google Chrome, Mozilla Firefox, or Microsoft Edge. Here's an article on how to record a customer payment.

Let me know if you have further questions.