GCE invalid grant on new resource creation

Hi! I'm trying to test out the gce functionality introduced in 1.3 and set
up a test instance of the develop branch.

I registered a new app in gce, generated a new cert and used this as the
mail/key pair for a new compute resource in my test foreman.

When I hit Load Zones, I get this:

Unable to save
Authorization failed. Server message: { "error" : "invalid_grant" }

and dropping into debug doesn't yield much else useful:

Started PUT "/compute_resources/test_connection" for 172.<redacted> at
2013-11-08 06:56:14 -0800
Processing by ComputeResourcesController#test_connection as /
Parameters: {"utf8"=>"✓", "authenticity_token"=>"<redacted>=",
"compute_resource"=>{"name"=>"gce-<redacted>", "provider"=>"GCE",
"description"=>"", "project"=>"concise-kayak-391", "email"=>"<redacted>@
"key_path"=>"/opt/foreman/lib<redacted>-privatekey.p12"}, "cr_id"=>"null"}
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."id" = ?
LIMIT 1 [["id", 1]]
Setting current user thread-local variable to admin
CR_ID IS null
ComputeResource Exists (0.1ms) SELECT 1 AS one FROM "compute_resources"
WHERE "compute_resources"."name" = 'gce-<redacted>' LIMIT 1
Google::APIClient - Initializing client with options
{:application_name=>"fog", :application_version=>"1.18.0"}
Google::APIClient - Initializing client with options
{:application_name=>"fog", :application_version=>"1.18.0"}
Rendered compute_resources/form/_gce.html.erb (214.3ms)
Rendered compute_resources/_form.html.erb (222.8ms)
Completed 200 OK in 434.9ms (Views: 224.1ms | ActiveRecord: 0.3ms)

Is this a foreman config issue or did I do something wrong gce side?