Hire a lawyer. If you cannot afford one, fix the website, call the attorney, respond to the complaint, plead poverty. Whatever you do, do not let it go to a default judgment.
It was a challenge as I tried calling to the number on the letter of intent to sue but was unable to connect so I thought it was a scam. About 6 months later I got a notice that a lawsuit has been filed. I had to update my site to make it compliant and then settle which was not good as we are a small business and unnecessary spending out of no budget is hard. Just get an app: there are free ones or about $50/mo that adds a widget to your site. This additional step can help you save from lawsuits.
I agree but the law is on their side and Shopify will not take responsibility. Best thing to do is try settling on your own. If you can prove them that you don’t have a lot of income and can only pay them certain dollar amount they should let you go. But definitely before trying to settle get the ADA widget and get a professional company to check your site for ada compliance and give you a report that your Site is fixed. Take that report report qs a proof that you now comply and try settling for $500. That is how much they pay to file the lawsuit. Very unfortunate ?? 
Aloha Smalia,
Sorry to hear that! Can you let me know the outcome?
This entire thread seems like a spam thread in order to promote an accessibility widget.
Whaaaaat??? How so??? I am a REAL PERSON with a REAL COMPANY who got sued…and i’m just trying to help other people out who may be in the same position. I am not an affiliate with accessibe, nor do I receive anything at all when another company uses the software. Just trying to help other people out.
We’re going through this now, Hiw did this work out for you?