Assuming that is all there is.There's two ways of getting an SSL certificate for use on a website:
1.) pay for a trusted one
2.) use a free one from Let's Encrypt that only lasts for 3 months at a time and hope that some janky backend script will work and auto refresh it each time.
Guess which path the owners of MK7 went? Snark aside, feel free to DM if you need help fixing this.
Good advice in general that everyone should practice. But has nothing to do with the lapsed SSL cert in this case.