This is likely due to Atlassian deprecating the ''basic auth'' plain password behavior in Cloud.
Deprecation of Basic Auth for JIRA/Cloud
As of June 2019, Atlassian Cloud users who are using a REST endpoint in Jira or Confluence Cloud with basic or cookie-based authentication will need to update their app or integration processes to use an API token, OAuth, or Atlassian Connect.
After June 5th, 2019 attempts to authenticate via basic auth (simple password) with an Atlassian account password will return an Invalid credentials error.
Get a ''token for your Link/Sync JIRA user:
Now, you need to use an API token to authenticate an Atlassian Cloud version of JIRA.
To set the JIRA connection properties for JIRA endpoints, open Chrome/browser and log in to JIRA/Cloud as the SYNC/LINK user.
Then generate an API token from your sync/link Atlassian account, then copy and paste it to the Password fields on the link.
For details on how to create an API token, see https://confluence.atlassian.com/cloud/api-tokens-938839638.html.
Then use that token INSTEAD of your password for that Sync/Link user when creating an App-Link.
For your Existing app-links:
Highlight a link on the ConnectAll HOME page, then click ''Load Application Link'', then scroll to the bottom of the page and ''Modify Application Link''.
Go to the ''Configuration'' tab and REPLACE the JIRA user password with the ''token'' string - this is your ''Link'' user.
Then go to the ''Entity Mapping'' tab ''Advanced Properties'' section and replace the ''sync password'' - this is for the ''sync'' user. (Usually, this is the SAME user as the Link user, but if not, this one also needs his own token).
To save you changes, do this:
Go to the ''Field Mapping'' tab then to the bottom and click ''Save''.
Do this for each JIRA-related link.