Display MoreCheck your logs. You find them here /srv/dev-disk-by-uuid-4e25905a-885d-4f57-81ce-5ffdc47d0304/appdata/swag/log/
Somehow ACME can't reach your Host/Swag-Container. Looking at your port-forwarding, you forward from your gateway port 80 to your docker hosting PC port 81 and from that to your swag-container port 80. It all looks ok.
Maybe the logs will shed some light on what the problem could be.
Your Nextcloud configuration needs some attention too. Don't use the subfolder in:
'overwrite.cli.url' => 'https://claredad.duckdns.org/nextcloud' ... this should only contain your URL:
'overwrite.cli.url' => 'https://claredad.duckdns.org'
You also need to set up an subfolder-config inside swag/nginx/proxy-confs. There is a sample for nextcloud there too.
But that has noting to do with the certificate. This is just FYI.
There are tons of instructions on the net how to do that. This also goes for nextcloud's config.php.
EDIT:
Your duckdns token is only used to update your IP via a dyndns-client like ddclient. It has nothing to do with the certificate.
I guess you have something like that already set up, either as a docker or on your gateway/router?
Thanks Bermuda. I played around for a while and finally got it going by creating a new domain called claredad2 on duckdns. work straight away.
Also thats for the heads up on my config file. I missed a few steps in the setup. Resolved now.