Browse in Incognito mode. if it is work in Incognito mode then got to normal normal mode and Clear browser cache and cookies then try
or
Go to
Tools > Site Health and check for REST API issues. If there is a REST API error, check your security plugins . Some security or optimization plugins may block REST API requests. Try disabling all plugins and then enable them one by one to identify the culprit.
or
Switch to a default WordPress theme (like Twenty Twenty-Four) and test.
or
Go to
Settings > Permalinks, change the structure, save, then revert and save again.
or
If you use a caching plugin (e.g., WP Super Cache, W3 Total Cache), clear the cache.