Error with the Quicksheet and a manually entered matrix of coefficients

It seems ployroots is sensitive to input methodology. The below works:

I experience no problems using Mathcad 15 M050

Unfortunately you don’t attach a worksheet, don’t say which version of Mathcad you are using or what the error message (the same as in the thread you link to?) you get is.

Needless to say - also the Quicksheet works as its should:

If you look at the last reply from Claudio in the thread  you linked to, you see that in his case the problem was solved by simply doing it again from scratch in a new session.