Show hidden sheets

I’ve to update a Calc document but can’t find a way to display hidden sheets.

I’m using LO Calc (x64) on a Windows 10 host.

The document I’m working with contains 7 sheets and only one of them is usable (it’s a form which sends submissions though email). I believe the other sheets contains the data that are feed into the form’s list, as shown in the Manage Names… section:

I can see there’s 7 sheet through the footer:

hidden sheets

However, from the Sheet menu, Show Sheet… is disabled:

unselectable options

Is there any way to access those sheets ? If not, if there any way to edit their content ?

EDIT: As mentioned by erAck, the issue was that the file was protected. Follow his answer and the comment he added to access the hidden sheets

Seems like the spreadsheet structure is protected, in that case Tools → Protect Spreadsheet Structure… is activated, select that menu item to unprotect it. It may be password protected.

Indeed the sheet was initially protected (and obviously our collaborator has left the company). I had to follow the procedure to unlock it (edit the table:protected= from content.xml).

I’ll follow this procedure and add an answer if I manage to access the hidden sheets

Note that the structure protection is a different thing than the protected sheet flag but basically stored the same in an ODF .ods document, just instead of <table:table ... table:protected="true" ...> it is <office:spreadsheet table:structure-protected="true" ...> (and table:protection-key and table:protection-key-digest-algorithm attributes).

Thanks for this crucial help !!! I finally managed to access the hidden sheets ! I’ll edit my question to add more precisions

I updated the FAQ entry adding the structure protection as well.

Your problem is different from the main topic of this question; you should ask it as a new question where it is more likely to get attention than in a question which has been marked as having a solution.