Sendgrid python lambda times out.

I'm trying to send an email from a lambda function via sendgrid.
When AWS runs the function it reaches sendgrid.send( message ) and then times out.
I've dramatically increased the time till time out to no avail.

Importantly, I have a second successfully running function.

The two lambda function have the same security groups, roles, permissions, etc.
(well - at least I haven't spotted it. my best guess is there's something here I don't know how/where to check for).
The two functions use the same layer for access to the sendgrid library.
I've checked api-key's multiple times.

The non-working function runs successfully when I run it locally.

Has anyone else come across this issue? How did you resolve it?

Thanks.