R - using intsvy package - pisa.reg.pv returning error ('a' must be a complex matrix) -

i using 'intsvy' package in r studio analyze pisa. replicating code else, wondering why following command not work (when works in other persons coding):

r0 <- pisa.reg.pv(pvlabel="math",                    x="vietnam",                   weight="w_fstuwt",                   data=devcon8a, export=false) 

i following error message:

error in chol2inv(qr$qr[p1, p1, drop = false]) :    'a' must complex matrix 

i double checked variables 'numeric':

class(devcon8a$w_fstuwt) #[1] "numeric" class(devcon8a$vietnam) #[1] "numeric" class(devcon8a$pvxmath) 5 different plausible values #[1] "numeric" 

"vietnam" dummy (numeric) created within data set. data set original downloaded pisa, filtered 8 developing countries (hence devcon8, including vietnam). previous coding same working off other person, whom 'pisa.reg.pv' working fine. have sth newer r version?

thank you.

try upgrading r , try executing update.packages().

if problem still persists, please post data in question can try assist.