I can't Find and Replace: Replace All- (Version: 6.4.4.2 (x64) Build ID: 3d775be2011f3886db32dfd395a6a6d1ca2630ff CPU threads: 4

I got a spreadsheet book for 12 months/sheets, each new sheet is thru a copy of the preceding sheet in which the referral formulas need to be updated in the current sheet. Usually, this worked fine with MS Excel and previous LibreOffice versions.

… What usually worked is replicating formulas taking into account the subtotals until the preceding month and brought in on the current month to have new subtotals in the current sheet/month.

Usually, this worked fine with MS Excel and previous LibreOffice versions.

What worked usually fine? You do not describe what you are trying to do in detail. What is your Find String, what is your Replace string, what other option set, what do you want to replace, what did you finally get when applying your settings (i.e. pressing button Replace All with your settings)?