Hello. Something’s wrong with the vendor section. please see the image below.
http://prnt.sc/el0iix
I guess you are using the vendors plugin, the issue is not coming from the wplms, so please try contacting the vendors plugin author for this issue.
ok. i deactivated it. how can i choose a vendor for a product then? i can't find any option field about vendor(seller of the product) on the product page.
Vendor is not a feature of wplms theme you have to use the third party plugin for it.