Problem with font and math environment

documentclass[a4paper,12pt,titlepage]{scrartcl}
usepackage{mathtools} mathtoolsset{showmanualtags}
usepackage{amssymb}
usepackage{newpxtext,newpxmath}

begin{document}sloppy
begin{align}
y=&Aleft[varTheta_{q}left[varTheta_nq_{h,n}^{frac{sigma_m-1}{sigma_m}}+(1-varTheta_n)q_{h,f}^{frac{sigma_m-1}{sigma_m}}right]^{frac{sigma_m(sigma_q-1)}{(sigma_m-1)sigma_q}}right.nonumber
&+left.(1-varTheta_q)left[varTheta_nq_{l,n}^{frac{sigma_m-1}{sigma_m}}+(1-varTheta_n)q_{l,f}^{frac{sigma_m-1}{sigma_m}}right]^{frac{sigma_m(sigma_q-1)}{(sigma_m-1)sigma_q}}right]^{frac{sigma_q}{sigma_q-1}}
end{align}
end{document}

It worked pretty well, until I’ve tried to use left[ … right] and the following was showed to me:

!pdfTeX error: pdflatex (file txexs): Font txexs at 758 not found
==> Fatal error occurred, no output PDF file produced!

I figured out that with changing the font from usepackage{newpxtext,newpxmath} to

usepackage{mathpazo} 
usepackage[scale=1.0425]{tgpagella}
usepackage[scale=.95]{tgheros}
usepackage{tgcursor}

there was no problem anymore, but I want to use the other font. How can I solve the problem?