App bridge not getting host param when installing app from partners page to a development store

[rohitmartires14]

So i tested my app from the link given by shopify-cli and it works fine.

i.e. 

https://123.ngrok.io/auth?shop=abc.myshopify.com

then after hosting it on vercel

i tried installing from the partners dashboard, app setting page 

more actions >> Test on development store >> install app

now this results in a link of the form:

https://foo.vercel.app/?hmac=bar&shop=buz.myshopify.com&timestamp=163750xxxx

and here the app does not get the host param, then app bridge just spits out errors
about missing host param

not really sure what to do here