Unable to switch to iframe in edge browser

Good morning,

i try to enter an iframe using the edge browser, but for whatever reason it will not work…
the iframe itself if found in the previous I.waitForElement() step but when i try to enter it using within() or I.switchTo(), i get the error:
The specified frame was not found in the current frame or window.

Does anyone have a clue how i can fix this? (it’s working in other browser fine)
Or what else i can try to access the elements within the iFrame?

thanks in advance,
Christian