Thanks for providing the additional information.
I apologize if this question seems basic, but you do have the opening php tag in your functions.php, correct?
Can you try temporarily switching to the Twenty Seventeen theme, and disable all plugins other than TEC and TEC Pro, and see if you still see the error? Also, make sure that Maps are disabled in the settings (Events > Settings > General > “Enable Google Maps”), and that the individual event does not have “show google map” checked in the Location settings.
Thanks,
Sky