This problem because your theme changed some line code of Shopify so please add one line with step by step:
Login admin page of your shopify
Open menu “Online store” and click “Edit code”, see image
Find file “product-template.liquid”, please check image.
Move to end of file and add this code edit your text after add to file product-template.liquid and save
<script> var inkgo_custom_lang = { personalize: 'Personalize design', photo_title: 'Photo', required: 'Please enter all text fields and upload images', upload: 'Please upload file JPG, PNG, JPEG, GIF', save: 'Confirm', change: 'Change', rotate: 'Rotate', }; </script>
Note: You only change text show in ”, for example ‘Personalize design’