TYPO3 Exception 1417988921¶
Below, the TYPO3 community may have provided additional information or solutions for this exception. However, these may or may not apply to your particular case. If you can provide more information, you should come back here and add your experience and solution steps to this issue once you have resolved it.
General TYPO3 troubleshooting tips can be found in the section "Troubleshooting" of the menu, and live support is available in the TYPO3 Slack channel #typo3-cms. (See How to get your TYPO3 Slack account.)
The CSRF protection token for the requested module is missing or invalid.¶
Page module not working (TYPO3 7.x - fixed in newer versions)¶
Create your first page in the List-tab. Afterwards it will work in the Page-tab too. Copied from this german thread: https://forum.typo3.org/index.php/t/210486/
Other Workaround, which applies for 7.4.0:
.t3d) a single leaf page from another TYPO3 CMS instance (mine was 6.2)
Right click root element in page tree => Import from .t3d (I imported only page properties)
Now I can append other pages to that page by using the New operation (which failed before)
I can even add pages (with New to the root element which did not work before.
Still, none of my pages is tagged as Use as Root Page in Page Properties > Behaviour => It does not have to do with "Root Page". Instead, at least one page must exist to get rid of the Bug (as a workaround).
Limitation: When I delete all pages in the page tree, and then try to right-click-New => I hit the error again. Basically this means that this workaround only works as long as you don't delete all pages.
See https://forge.typo3.org/issues/66704. When there is a fix available and released, an update should do.