Iframe 406 Error

I’ve created a page called Payment and added it to client portal.
I added the iframe code into the “payment” page. When I go to that page directly, I can see the iframe. But when I send an invoice or quote to a client (myself) the link on the e-mail doesnt work and the client gets 406 error.

If you want to send a sample link to contact@invoiceninja.com I can try to debug the problem.

Thank you. Ive sent an invoice to your mail.

Please email a “view in portal” link

Invoice had a view in portal link in it but Ive sent a seperate one again

Please click “view source” on the invoice page and send the relevant iframe code.