Service invoked too many times for one day: urlfetch

[Jay Scott]

Hoping this is the right place to post but if not, please let me know.

In Google Sheets, I understand the quota limit for gmail.com users to be 20k requests per day.  I'm only doing a few hundred, maybe a few thousand on a really intense day once in a blue moon, and yet I'm constantly getting this message when I try to use the importJSON() function (which uses urlFetch).  My spreadsheet is set to recalculate only on change.

Does anyone know what would be causing this?  I've also tried accessing the same spreadsheet from 3 different gmail accounts, and all 3 get the errors instantly so whatever this is, is not per-user-account.  Appreciate any insights on this!