secret access link not working on some pages

Hi,

I am using the WP maintenance plugin for my coming soon page which is currently enabled.

When visiting the rest of the site via the secret access link https://www.hundetraining-mit-roya.at/?my1test some pages are still loading the coming soon page. This is inconsistent for different devices/users.

I have enabled browser cache in W3 TC. Does this interfere with the WP maintenance plugin?

I tried “Purge all caches” from Performance at the WP admin top bar but it didn’t make a difference.

I now tried “Empty cache” at WP Sidebar > Performance (I forgot where exacty) and it made the page work on my iPad as normal.

Is there a difference in these 2 settings (Purge all caches and Empty cache)?

How can I fix this problem?

Thanks!