formatting suddenly unavailable in pages 11.1 (paragraph and character styles, master slide)

Hey. I am in urgent need of support on the following issue :

For the past few weeks, I have been writing on a term paper - which includes a lot of formatting, especially of footnotes and paragraph styles to generate and update my table of contents. It all went

well until all of a sudden, for some unfathomable reason any kind of editing styles and (generalised) formatting became "unavailable" (as in greyed out) :

• I can't create new styles nor edit the ones I already defined (paragraph and character styles).

• I can neither create nor edit master pages nor move an object to the section master.

• Footnotes (not endnotes!) are not recognised as such if I tap them once as to edit the paragraph style. Yet, if I select one specific footnote, it does recognise its predefined style.

• I cannot arrange (align, flip, group or distribute) objects (including text) and once I try to change spacing or indents, it all goes haywire.

Attempts to no avail : setting "make master object selectable" on and off, same for "facing pages" and "document body". Then duplicating the file twice, converting it to page layout respectively pages ` 09.

Further information : My MacOS is up to date (Big Sur 11.4) and I am its only user hence admin. The document is not locked and Pages is granted full disk access.

I have been using Pages for ages, never having had difficulties of finding an explanation to its seemingly odd behaviour every so often. I am so very desperate right now because I need to hand in my paper today and would appreciate any hint on this issue; I'm rather convinced the solution is going to be a strikingly obvious one. Thanks in advance!