Summary Report - No Longer Able to Summarize by ""Total

I have a summary report I have been using for years to calculate totals using a formula. Suddenly I am not able to summarize by "Totals" (it defaults to "Distinct Count" with no options available). But, when I access the report using my phone, I am able to select summarize by "Totals" (and all options are available). Any ideas? Thanks!