As @heather said, @matthew.fuller526, we are no longer developing or supporting the Envelope Budget. I peeked at the template and the code and didn’t see an obvious reason the formulas & scripts wouldn’t work down to row 270. You might check the named ranges in the spreadsheet to see if one of the ranges ending in AdjustBudgetRange has been trimmed down to the limited range you mention.
Please switch to the Savings Budget which is built for compatibility with more recent conventions.