Thanks for the suggestions - but still no luck. I have tried this in both Chrome and Firefox (I usually use Firefox and have had no problems until this).
Have you been able to fix this? I contacted hubspot support they said everything looks fine on their end so issue must be on my end, they can help further. But I tried everything and still same issue.
The suggestions that Hubspot gave were to use Chrome, clear the cache, disable all add INS for the browser, and to try accessing in private mode. So I'm guessing that you have been told this, but with no success ( like for me)
What eventually solved the problem was disabling (initially) the ad blocker component of my anti virus software - as it was this that was blocking access (hence why it was a single page where l had the problem).
I then added Hubspot to the ad "white" list on the avs and it has worked fine since then.