Your sheet uses function names like R', r', Psi', etc. with the apostrophe as a normal character which is part of the name.
It looks like the converter interpreted the apostrophe in the solve block equations as the derivative operator which causes the error.
Solution is to delete each of the wrong derivative apostrophe and retype a 'normal' one.
I did so in the first failing solve block in the attached sheet.
Replacing the apostrophe is only necessary in the function names, not the variable names!
Next error is a unit mismatch but this would also have failed in real Mathcad. The program for Check_weld compares a dimension-less scalar (D.fillet_,max) with D.reqd which is of dimension area per force (!?). This won't work.
Prime 9 sheet attached
P.S.: It looks like we had discussed the very same problem (apostrophe in function names) already here: Issue with solver block
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