OK: this is a PGI-compiler-configuration problem: your library uses single trailing underscores for nf_put_att_int__ etc., whereas in the I/O API compile pgf90 is generating double trailing underscores.
[There are various Makeinclude.pg to go with various C-compiler choices…]
You need to make sure that your ioapi/Makeinclude.$BIN has the following, so that pgf90 does not generate double trailing underscores:
FOPTFLAGS = -O2 -V -Mnosecond_underscore