I have tested everything, also with disabling all plugins.
Only when changing the form with elementor the form is shown once:
1 change form
2 empty all cash
2 publish
3 empty browser cash on other pc
4 load page, form shows once
5 refresh page
7 empty screen
I can view the form, but when I click submit without entering anything in it (should fail validation) the form disappears. When I go back, the form shows up again.
It appears you have some issue with the form validation. On the validation page, the CSS rule display: none is added to the form element (see screenshot). You’ll need to determine why the display: none CSS is added to the form when it’s validated. It’s likely a setting in the GF form or Elementor.
I had the same error because the form shortcode was embedded in an Elementor text widget, which worked until recently. Now it seems that the form shortcode in Elementor has to be embedded in a shortcode widget. This allows the forms to be displayed again.
We had a support ticket yesterday where it was confirmed Elementor 3.26 includes a breaking change to the text widget. Using a shortcode widget does seem to be the way to go until Elementor can resolve the issue.