Contacts not getting added via API anymore after upgrading Mautic version?

Your software
My Mautic version is: 2.16.3
My PHP version is: 5.6.29

Your problem
My problem is:
I recently upgraded my Mautic version to 2.16.3, didn’t upgrade in a while, but I noticed as soon as I did it doesn’t look like my contacts gets saved to my lists properly through the API anymore.

These errors are showing in the log:
[2020-08-08 22:49:22] mautic.ERROR: Uncaught PHP Exception Symfony\Component\HttpKernel\Exception\HttpException: “signature_invalid” at /var/www/vhosts/ line 244 {“exception”:"[object] (Symfony\Component\HttpKernel\Exception\HttpException(code: 0): signature_invalid at /var/www/vhosts/"}

Steps I have tried to fix the problem:
I tried clearing my Mautic cache, but still having the same issue. Reaching out to the community to see what other steps I can take to resolve this issue.

Thank you!

Ok, I was able to fix it; I ended up also updating the “api-library” and now it works again.

Thank you!