Custom Images don't show up in 1.12.2 2020.5 generator plugin!

I am currently using 2020.5, but also using the 1.12.2 official plugin for reference

When I open GUIs by procedures on items or by right clicking mobs, I want to open up GUIs that mostly use custom images. These guis were made back in 2020.2 before I installed 2020.5 and the plugin. Now, when I try to open them, the images appear for a frame, and then disappear except for buttons and titles prebuilt into the generator. Do I need to redownload the images or something? Thanks!