Hi,
If your origin server does not return any data after 100 seconds, Cloudflare will close the connection and serve a 524 error. This can happen if your server is simply taking too long because it has too much work to do - e.g. a large data query like importing 75.000 subscribers, or because the server is struggling for resources and cannot return any data in time.
First thing to check is if Acymailing has any database issues. You can perform a database integrity check in Acymailing->Configuration->Security under thge Advanced section at the bottom of the page. In case you encounter any issues these must be resolved first. If the check is OK, you can proceed with the following information.
I'm not familiar with Cloudflare, but I believe you can implement status polling of large HTTP processes to avoid hitting this error.
Alternativly you can temporarely disable Cloudflare for your backend pages (url's containing wp-admin (Wordpress) or administrator (Joomla) ). After that try to run the import again. This way you can see what actuallkty is happening on your server.
Once you have succesfully imnported your cms users we recommend to enable the cms intergation in Acymailing. This way a new subscriber will be added eacht time a new cms user is created, so you never have the run this large import again.
You can enable the user integration in Acymailing->Configuration->Subscription and it's documented here: https://docs.acymailing.com/setup/configuration/subscription#user-integration
Note that enabling this integration does not automaticly import existing cms users. You still have to run the import once. But after that users are automaticly synced between your cms and Acymailing.
Please don't forget to enable Cloudflare for your backend pages again once you're finished.
If you need any further assiistance, please let us know.
