Using external shortcodes in input elements that fully typed out

On our existing site, we have a lot of form elements that are already typed out fully, i.e.:
<span class=”wpcf7-form-control-wrap dynamichidden-480″><input type=”hidden” name=”dynamichidden-480″ value=”[first_name]” /></span>

We have a custom plugin that was written for us which runs the “first_name” shortcode. On a dev site, which is an exact clone, I’ve turned off the old custom plugin and have written my own that does the “first_name” shortcode. However, in these forms, it does not change the “[first_name]” accordingly. I can replace those lines with the proper dynamic field shortcodes, but that’s a lot of lines to replace…

I’ve tried using wpcf7_form_elements filter, and the plugin Contact From 7 Shortcode Enabler, but neither of those worked either. Does anybody know what I’m missing to make my plugin work with CF7/Dynamic Text fields?