LetsEncrypt errors with external subdomain

[marcelo4k]

Hello,

I cannot add a LetsEncry certificate to externally pointed subdomains.
For example:
-mydomain.com is in HappyHosting
-I point A record for subdomain.mydomain.com in HappyHosting to CloudHosting, where I have my VestaCP
-I add subdomain.mydomain.com to my VestaCP webs
-I check the box for LetsEncrypt and I get an error

Can this be achieved by redirecting some "acme-challenge" like folder to mydomain.com in HappyHosting via .htaccess?

Best,
Marcelo