OAUTH Custom Connector Works in PowerBI but gets "Invalid connection credentials" Error

[Thinker]

Here is what I have done:

- developed a working OAUTH Custom Connector for PowerBI.

- added it to my data gateway.

- added "TestConnection" to my connector to make it compatable with the gateway.

- tried to configure the gateway with my custom connector

I am getting this error:

Unable to connect: We encountered an error while trying to connect to . Details: "We could not register this data source for any gateway instances within this cluster. Please find more details below about specific errors for each gateway instance."Hide details
Activity ID:	de69c3a6-xxxx-4fef-ad29-f465ffcad197
Request ID:	eb287652-xxxx-418e-cba9-dee9f2065aab
Cluster URI:	https://wabi-canada-central-redirect.analysis.windows.net
Status code:	400
Error Code:	DMTS_PublishDatasourceToClusterErrorCode
Time:	Thu Jul 04 2019 11:57:56 GMT-0700 (Pacific Daylight Time)
Version:	13.0.9933.268
xxxxxxxxxxxxxx:	Invalid connection credentials.
Underlying error code:	-2147467259
Underlying error message:	Credentials are required to connect to the xxxxx source. (Source at {"url":"{\"url\":\"https:\\\/\\\/xxx.xxx.xxxxxxx.xxx\\\/xxxx\\\/v1\\\/legacy\\\/lists\\\/xxxxx\"}"}.)
DM_ErrorDetailNameCode_UnderlyingHResult:	-2147467259
Microsoft.Data.Mashup.CredentialError.DataSourceKind:	xxxxxxxxxxx
Microsoft.Data.Mashup.CredentialError.DataSourcePath:	{"url":"{\"url\":\"https:\\\/\\\/xxx.xxx.xxxx.xxx\\\/xxxxxxx\\\/v1\\\/legacy\\\/lists\\\/xxxxx\"}"}
Microsoft.Data.Mashup.CredentialError.Reason:	CredentialMissing
Microsoft.Data.Mashup.MashupSecurityException.DataSources:	[{"kind":"xxxxxxxxx","path":"{\"url\":\"{\\\"url\\\":\\\"https:\\\\\\/\\\\\\/xxx.xxx.xxxx.xxx\\\\\\/xxxxxxx\\\\\\/v1\\\\\\/legacy\\\\\\/lists\\\\\\/xxxxx\\\"}\"}"}]
Microsoft.Data.Mashup.MashupSecurityException.Reason:	CredentialMissing

CredentialMissing seems like a pretty specific error except that the credential shouldn't be missing.  Also, the URL seems to be using more escape slashes than it should need.  My .Contents function accepts a text parameter which is the only thing I can think that might be causing this but I haven't been able to fix it so far with several different type conversion attempts.

Any ideas?