As I write this I sincerely hope you have found something worthwhile already. However in case you have not I am guessing with your experience you can still go on to be
A) something like a product architect somewhere in a big firm
B) A strategy/ senior role in a startup but working as an employee
C) Try your luck again at a startup ( 3 could be the charm)
Pushing 40 and coming from a startup background is tough. I know since I was involved in quite a few and they are all gone. Ultimately i ended up learn things like python, SQL, SPSS and stats in my late thirties so I could apply for and be relevant in my current role in a firm (i'm an employee now ).
It's a lot of luck, and constant persistence to get back into the mainstream. However it does happen over time . Some steps which could help you are
A) increase your visibility to any potential employers via any tools available
B) Increase your appeal to them which helps them see value
C) A and B done right will cause them to ask around about you at least.
D) A,B and C done right might result in an offer
Good Luck