https://docs.gitlab.com/ee/user/profile/personal_access_tokens.html explains how to create tokens.

Can you check if you see any error in AEM logs or the browser?

rep:restrictions will be useful for Closed User Group (CUG)

Ensure you use a sample wknd project compatible with the AEM version.https://experienceleague.adobe.com/docs/experience-manager-learn/getting-started-with-aem-headless/spa-editor/react/overview.html?lang=en is compatible with AEM as cloud and AEM 6.5.4+.

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Please refer : https://experienceleague.adobe.com/docs/experience-manager-65/administering/introduction/tc-manage.html?lang=en

Can you check if Replication Queue is configured correctly?

Please refer : https://developer.adobe.com/developer-console/docs/guides/authentication/ServerToServerAuthentication/migration/

Try opening the URL in Chrome Incognito mode or clear browser cache.

https://experienceleague.adobe.com/docs/experience-manager-learn/assets/advanced/asset-insights-launch-tutorial.html?lang=en might help.