I used Postman to check if the API works and got this error.
The configuration is as follows
Error message = Unexpected type of JSON object member with key "sub".
Endpoint = https://suchica.atlassian.net/rest/api/3/myself
Authentication method = Bear Token
Access Token = eyJhbGciOiJIUzI1N.......... .eNPQT1AkZt5Ftqtod8
Scope = read:jira-user
The endpoint was not correct.
This is because I think I use OAuth 2.0 (3LO), so I need to use the latter one.