ChatGPT, a large-scale language model, holds significant potential for providing consistent and timely feedback, thereby offering comprehensive support across various dimensions of writing. However, existing research is limited in its exploration of the specific impact of ChatGPT's written feedback on English as a Foreign Language (EFL) learners with low language proficiency. This study delves into the effects of ChatGPT feedback on such learners, utilizing data from prompt-feedback interactions and subsequent interview analyses. The findings reveal that the essay reviewing process, involving interactions with ChatGPT in English, posed substantial challenges for the learners. Additionally, the study suggests that ChatGPT's written feedback has limitations in effectively enhancing the writing skills of learners in this proficiency category.