Cloudflare with Zapier and Wordpress

I am tried to connect Buffer to WordPress with my website hosted on Cloudflare.
Buffer connected through Zapier and then to the WordPress Zap.

The Zapier plugin used to communicate to WordPress via XML-RPC but things have moved on.
Communication is now via REST API to WordPress from Zapier creates the following error:

authentication failed: Got 401 calling POST https://example.co.uk/wp/wp-json/zapier/v1/token, triggering auth refresh.

When I look into Cloudflare and REST API V4 is mentioned. As you can see the error code mentions REST API V1.

Any ideas please?

Have you blocked access to your XML-RPC due to security reasons?
Do you have some security plugin installed like Wordfence Security?
Using Cloudflare Firewall?

Are you blocking your REST API access?
Or allowing only to autenticated user with granted rights /password to access it?

Have you tried contacting Zapier about your issue?
You can contact them here: Zapier Support.

Zapier’s Troubleshooting documentation.

Have you checked this one?:

Hi fritexvz

I have not blocked any mode of communication. I understand that XML-RPC is redundant now.

I managed to test my website using some REST API tools and successfully tested GET and POST. So I believe the problem is either with the Zapier WordPress Zap or the Zapier Plug-in.

I changed nothing on the security setup on my website during the test.