Permissions question: Flow --> Sharepoint Add-in, item level security

[bennet]

I am trying to read and write item level security in sharepoint online with Flow.  I have followed numerous examples.  I have even used tenant admin to give tenant Manage permissions through the Sharepoint Add-in.  I can successfully retrieve an access token, but no matter what combination of access permissions I give, Flow returns a Forbidden error when trying to read or update item level security.

I know that Flow uses the Sharepoint\App account, do I need to do something special with that account? 

https://xxxxx-admin.sharepoint.com/_layouts/15/appregnew.aspx

https://xxxxx-admin.sharepoint.com/_layouts/15/appinv.aspx

Permission scope:

<AppPermissionRequests AllowAppOnlyPolicy="true">
<AppPermissionRequest Scope="http://sharepoint/content/tenant" Right="Manage" />
<AppPermissionRequest Scope="http://sharepoint/content/sitecollection" Right="FullControl" />
</AppPermissionRequests>

I post to "https://accounts.accesscontrol.windows.net/xxxx/tokens/OAuth/2"

I receive an access token

I use the token to post to https://xxxxx.sharepoint.com/sites/xxxxx/_api/lists/getbytitle('xxxxx')/items(1)/roleassignments/

I get Access Denied

I even get access denied if I try to get the site title ("https://xxxx.sharepoint.com/sites/xxxxx/_api/web?$select=Title")

What am I missing?

Thanks in advance

[Pieter_Veenstra · Accepted solution]

Are you using the http request action from the sharepoint connector or the one from the http connector?

[bennet]

I'm using the HTTP connector. 

Should I be using the "Send an HTTP to Sharepoint" connector?

[bennet]

I changed the HTTP connector I'm using to the Sharepoint HTTP connector and I'm starting to see some good results.  I believe this may be the solution.  

Thank you for pointing me in the right direction.

[Pieter_Veenstra]

The SharePoint version handles all the painful authentication troubles.