Cannot Create or Edit any post or page

I have 4 websites. 2 of them I cannot create or edit any page or post. One is using elementor and the other one Astra. My other 2 sites are ok, elementor and spectra. Whenever I click on add new post/page, I get a blank page – nothing – no menu whatsover. I tried it in Chrome and Firefox and I get the same issue. They are all updated. What should I do? TIA