Hey Heinz,
We are currently working on resolving an issue between WordPress 6.6 and the display of the Ninja Forms submissions page. Your submissions are still being recorded normally. It is only the display of the page itself in the WordPress admin that has been temporarily impacted.
Please accept our sincere apologies for the hassle this causes. We have identified the root of the problem and a solution. We’re working now to validate that fix and release it. Look for an update soon that resolves it.
If you need to access submissions immediately, please navigate to Ninja Forms > Settings. Under Advanced Settings, check “Show Legacy Submissions Page”, then save and refresh the submissions page.
Give it a try, and let me know how that goes! 😀
Thank you
Faisal