Check if you are the onwner of that spreadsheet or, at least, have editing permissions for your account.

Otherwise, get in contatct with Manychat's Support Team. You can do it via support@manychat.com or open a ticket at https://help.manychat.com/

Did you ever get your answer?

I tired to submit a request but the site didnt let me.  It just wants me to look at articles.

i’m having similar issue where I’m getting permission issue and cant see any of my google sheets when trying to insert row.

I seems i have refreshed permissions and checked if i’m the editor of the sheet.  I do not know what else to do.  Please help.