The OP explains above:
Once I removed the ST app Amazon Alexa from the one hub (v1 hub) all the devices from my main ST hub were discoverable.
There is no fix if you are trying to connect two SmartThings hubs to Alexa, even if it is two different Amazon accounts. ( such as if you have a main home and a relative’s home both as locations on one smartthings account, you each have an Alexa account, and you try to add Alexa at each location.)
Basically even though smartthings allows you to have two locations on one account, this will confuse echo.
There’s an official support statement that says they are working on this feature, but don’t get excited about that: it’s been the same statement for three years now. 
Can I control multiple SmartThings Locations with Alexa?
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No, not at this time. But we are working on an update that will allow multiple Amazon Alexa devices on separate Amazon accounts to control separate SmartThings Locations.
https://support.smartthings.com/hc/en-us/articles/207808076-Amazon-Alexa-SmartThings-FAQ#Locations
So basically each hub has to have its own smartthings account and its own echo account if you want Alexa control to work with SmartThings, only a one to one correspondence is allowed at this time.