I had an issue using two PC's on one the =LINEST(yrange,xrange^{1,2}) worked fine, on the other it did not, I got one result not three. What I found was on the second PC it was inserting an invisible @ character that stopped the array working properly. If I copier the sheet an put it on PC 1 I could see the character and delete it. Save the file and put it back on the 2nd PC and supprise it worked properly. Haven't found the cause yet but suspect there is a windows or excel setting different, but it wasn't the region, language or keyboard settings. There are differences between the PC's one is running 1st is running office 365 the 2nd is running excel 2019 stand alone. The Line on the bad PC read

=@LINEST(yrange,xrange^{1,2}) but you couldn't see the @ on that PC but it screws thing up..