WordPress Login Issue Fix

I need help fixing a login issue on my WordPress website caused by a plugin error. I cannot access the admin panel, and I believe customers are also unable to log in. The goal is to identify the root cause, resolve the login problem, and restore normal access for both admin and customer accounts. Please share your experience with similar WordPress login issues and your approach to troubleshooting and fixing them. I do not have a large budget for this job so if you can suggest a price that would be very helpful.