Snapchat Says "Device Banned" With SS06 Error

I have been unable to log into my Snapchat account for approximately three months. Every time I try to access the app, I receive the message "SS06 error, your device has been banned," and I am completely locked out of my account. I believe this situation stems from someone else having accessed my account without my permission at some point in the past.
Despite trying numerous steps — uninstalling and reinstalling the app, changing my password, switching to different internet networks, and trying different devices — nothing has resolved the issue. I have also contacted Snapchat support repeatedly but have not received a single response to date.
Because my account contains personal information and memories that matter to me, this lockout is causing me serious harm. I am requesting that both the account ban and the device ban be lifted, that my account be secured again, and that I receive a clear and direct explanation of the reason behind this block.