Negative data_PDx run

Hello ALL, I am using PDx along with NONMEM to conduct a META analysis, but I have negative values in my DV column. PDx cannot deal with this and gave me the following error message; “The table file did not get created by NONMEM. It is possible that an error occurred in the NONMEM run which was not output to the screen or that the code required to create this table was not found in the control file” PS: when I removed the negative sign from the data in my DV column, PDx was able to process the data but it gave a strange results! Is there any way to deal with these negative data? Thank you.