REGARDING COMBINING VARIANTS IN CLOUDMAP IN GALAXY

Hi
I am new to sequencing and i tried with galaxy i am done with vcf files of all mutants and now i have to combine variants but its showing error the tool is as follows
https://usegalaxy.org/root?tool_id=toolshed.g2.bx.psu.edu/repos/devteam/variant_combine/gatk_variant_combine/0.0.4
Please help what is wrong and how i can correct that