Can't create SSL cert after DNS change

Hi,

I've both a server (SERVER_1) and DNS (DNS_1) records running on linode.

Before:

I had various subdomains registered as A records. I ran certbot on my linode server to generate SSL certs, and used the dns-linode authenticator, which worked fine after it created TXT records.

Now:

I have grown some of the site functionality to an external server (SERVER_2) with its own DNS (DNS_2). The API remains on the same linode server (SERVER_1) as before, with an A record on DNS_2 pointing to my SERVER_1 IP address by api.mydomain.com

SERVER_2 also auto-generates SSL certs and has 2:
1 for mydomain.com and 1 for *.mydomain.com

The Problem:

I cannot find a way to generate an SSL cert on the linode server for api.mydomain.com. dns-linode authenticator is failing.

Although SERVER_2 tries to generate an SSL cert for all * subdomains I believe I'm correct in thinking I need to host a cert for api.mydomain.com on SERVER_1 as that's where the A record points to.

Details

Running the same certbot command that worked before now informs me that:

Certbot failed to authenticate some domains (authenticator: dns-linode). The Certificate Authority reported these problems:
Domain: mydomain.com
Type: unauthorized
Detail: No TXT record found at _acme-challenge.mydomain.com

I can see in cloud.linode.com that TXT records were generated.

Question

I'm a bit lost as to what it is I need to change to get an SSL cert functioning again on SERVER_1. I'm running nginx in a docker container so my attempts to do a standard certbot installation weren't relevant. If I got confirmation this would be the way to go, I could look at roundabout ways of working with a containerized nginx cert.

Also, I'm not entirely sure why the current dns-linode is failing with the change I made. Although the initial request is not on DNS_2, it points back to SERVER_1 (and I thought it also pointed to DNS_1). TXT Records are being created by the authenticator.