Submit button not working for one user

A user has contacted me to say that he is unable to submit comments. When he clicks the “Submit” button, the button changes color, but the comment is not submitted.

I have only heard from one user about this — it seems to be working fine for everyone else, as far as I know.

Any ideas about what might cause this? Something on the user’s end? (He’s using a mobile device.) Or a setting on my end that might effect a small percentage of users?

Any help would be appreciated. Thanks!

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