SUMPRODUCT returns 0

Question

I have the following SUMPRODUCT formula: =IFERROR(SUMPRODUCT(SUMIFS(INDIRECT("'"&rngWorksheets&"'!"&H$26),INDIRECT("'"&rngWorksheets&"'!$L:$L"),$Q$5,

INDIRECT("'"&rngWorksheets&"'!$M:$M"),$B11)),)

It had worked as it should for years, but now it returns a value of 0. The calculation is set to Automatic; if I select Calculate Sheet the correct value is returned, but if I save the workbook the value reverts to 0.

Below are the final three steps in the Evaluate Formula process. Removing the "IFERROR" function has no effect, a value of 0 is returned. I can't understand why the correct value of 3365.5 is not returned.

Any insight would be appreciated.

Thanks.