@jaypreet
Hello,
This is usually caused by a few various things. since it does not look like you are using SSL, I’ll skip the debugging for that.
Please start by deactivating all plugins except WooCommerce, WC Vendors and WC Vendors Pro.. then test. Let me know if this resolves the issue, as often a plugin conflict is the issue for image uploading.
Secondly, you can try logging in as a vendor via the my-account page. Do not use a special form for logging in.