Your theme or another plugin is causing it.
Try this:
https://www.fastsecurecontactform.com/submit-button-missing
Try this:
WordPress: It could be the theme you are using is causing it
Do this as a test:
In Admin, click on Appearance, Themes.
Temporarily change your theme to the stock theme:
“WordPress Default” (default for WP version 2.0+)
“Twenty Ten” (default for WP version 3.0+)
“Twenty Eleven” (default for WP version 3.2+)
“Twenty Twelve” (default for WP version 3.5+)
It does not cause any harm to temporarily change the theme do some testing and then and change it back.
Does it work properly with the default theme?
If it does then the theme you are using is the cause.
WordPress: Maybe another plugin is conflicting.
Look on the Admin – Plugins – menu.
Temporarily Disable (not uninstall) all your other plugins.
Does it work now? If yes, Activate the plugins one at a time, test to determine
which one conflicts. Which plugin was causing it?