The Send chatMessage in channel endpoint returns 401 Unauthorized even though the token is valid.
In addition, list chats has the same issue.
Send chatMessage in channel API ref: https://learn.microsoft.com/en-us/graph/api/channel-post-messages?view=graph-rest-1.0&tabs=http
List Chats API ref: https://learn.microsoft.com/en-us/graph/api/chat-list?view=graph-rest-1.0&tabs=http
We already confirmed required permissions are given.
Failed request (Send chatMessage in channel):
Graph Explorer:
https://developer.microsoft.com/en-us/graph/graph-explorer?request=teams%2F321f6a10-19f2-4e89-a8a4-67b07bd8f189%2Fchannels%2F19%3A579884d012a34058b3ab9224a8d5051a%40thread.skype%2Fmessages&method=POST&version=v1.0&GraphUrl=https://graph.microsoft.com

Curl:
> curl -v -k --request POST 'https://graph.microsoft.com/v1.0/teams/321f6a10-19f2-4e89-a8a4-67b07bd8f189/channels/19:579884d012a34058b3ab9224a8d5051a@thread.skype/messages'
> --header 'Authorization: token_ommited_as_it_is_still_valid_now'
> --header 'Content-Type: application/json'
> --data-raw '{"body":{"contentType":"html","content":"<div><div>jdnd</div></div>"},"mentions":[],"attachments":[]}'
Response:
- Mark bundle as not supporting multiuse
< HTTP/1.1 401 Unauthorized
< Transfer-Encoding: chunked
< Content-Type: application/json
< Strict-Transport-Security: max-age=31536000
< request-id: 725acdca-123a-47a5-92dc-247aeeb426cf
< client-request-id: 725acdca-123a-47a5-92dc-247aeeb426cf
< x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"Japan West","Slice":"E","Ring":"2","ScaleUnit":"002","RoleInstance":"OS1PEPF00005643"}}
< Date: Tue, 21 Jun 2022 01:55:28 GMT
<
- Connection #0 to host graph.microsoft.com left intact
{"error":{"code":"Unauthorized","message":"UnknownError","innerError":{"date":"2022-06-21T01:55:28","request-id":"725acdca-123a-47a5-92dc-247aeeb426cf","client-request-id":"725acdca-123a-47a5-92dc-247aeeb426cf"}}}
A counterexample using same token: Request to /me endpoints
Request:
Graph Explorer:
https://developer.microsoft.com/en-us/graph/graph-explorer?request=me&method=GET&version=v1.0&GraphUrl=https://graph.microsoft.com&requestBody=eyJib2R5Ijp7ImNvbnRlbnRUeXBlIjoiaHRtbCIsImNvbnRlbnQiOiI8ZGl2PjxkaXY+amRuZDwvZGl2PjwvZGl2PiJ9LCJtZW50aW9ucyI6W10sImF0dGFjaG1lbnRzIjpbXX0=

Curl:
curl -v -k 'https://graph.microsoft.com/v1.0/me'
--header 'Authorization: Bearer token_ommited_as_it_is_still_valid_now’
Response:
- Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Cache-Control: no-cache
< Transfer-Encoding: chunked
< Content-Type: application/json;odata.metadata=minimal;odata.streaming=true;IEEE754Compatible=false;charset=utf-8
< Strict-Transport-Security: max-age=31536000
< request-id: 3829ad44-6806-40cb-9854-a60e4544e25c
< client-request-id: 3829ad44-6806-40cb-9854-a60e4544e25c
< x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"Japan West","Slice":"E","Ring":"2","ScaleUnit":"001","RoleInstance":"OS1PEPF0000566D"}}
< x-ms-resource-unit: 1
< OData-Version: 4.0
< Date: Tue, 21 Jun 2022 01:57:52 GMT
<
- Connection #0 to host graph.microsoft.com left intact
{"@odata.context":"https://graph.microsoft.com/v1.0/$metadata#users/$entity","businessPhones":[],"displayName":"sync test 010","givenName":null,"jobTitle":null,"mail":"<censored>","mobilePhone":null,"officeLocation":null,"preferredLanguage":null,"surname":null,"userPrincipalName":"<censored>","id":"14e06f7c-57ac-424a-be45-63504546b6a2"}