First, identify if this is affecting all Capture end users or just one end user? There could be an issue with the end users internet/network as if the Access Support team are able to access the web page ok.
Try another web browser to see if the Access Capture link works.
For general troubleshooting steps, see:
https://kinsta.com/knowledgebase/this-site-cant-be-reached/#:~:text=Restart%20your%20internet%20connection.,Flush%20your%20DNS%20cache.
Finally, add Capture to your exceptions list on your firewall if you look after your own servers and they are not hosted by Access.
