Short Codes Not Working - Wistia and GetResponse

I just installed the Wistia and GetResponse plugins, both of which use short codes to allow me to post content with them. However, regardless of what I do these short codes return no results. I am able to use the typical iFrame for Wistia, but GetResponse is now totally unusable. My theme hasn't been updated in a while (custom design, no longer being supported). Is there some code necessary to activate short codes? I did update all my plugins to no avail. I have also confirmed that my theme does have the necessary header/footer hooks. Are there any troubleshooting tips you can offer to help me solve this problem?