Please, more information! We are mostly old geeks and terrible at guessing! That information is critical to how we advise you to proceed.
What Mac Model and sub-model? Do you remember what macOS version it was running?
See: If your Mac starts up to a circle with a line through it - Apple Support
The reason that the sub-model is important is that it contains a year, and older Macs cannot use the recovery partition mentioned in the article. We'll need to try something different if that is the case. But we need that extra information.