Problem:
Count number of entries in repeating field group return 0

Solution:
To get total count based on repeating field group items, you will require to use the post relationship API function toolset_get_related_posts().

You can find proposed solution in this case with the following reply:
=> https://toolset.com/forums/topic/count-number-of-entries-in-repeating-field-return-0/#post-2067453

Relevant Documentation:
=> https://toolset.com/documentation/customizing-sites-using-php/post-relationships-api/#toolset_get_related_posts