Problems sharing an Excel 365 workbook between Windows and Mac

Hi, I constructed an excel 365 spreadsheet on my Windows laptop which included the indirect formula within it. It all worked well. i shared the workbook with a colleague who uses Excel 365 for Mac on a Macbook Pro. He was also able to use the workbook without any problems - until last week. Now the sheet has lost functionality and when I investigated all the indirect references within the formulae had changed to the following -

=_xlfn.ANCHORARRAY(INDIRECT(D4))

Why has this happened.  I tried correcting the formula in his copy but this does not work.  How can this issue be resolved