I have installed the 2020 trial but when I start it, all it says is that an error occurred

You can send them an e-mail at tcssup@adobe.com - I think it's because your corporate environment has blocked the port that Adobe uses to "phone home" for activations. But only the RH folks will be able to tell you which one needs to be freed up. So feel free to ask for help.

Do you have a restricted Internet connection? The program does a "phone home" each time it starts up to check. If that's the case (a restricted Internet connection) you'll have to get Adobe Support to help you out as Peter says.

Yes but did you install RoboHelp with admin rights?

If you did, then you need to reach out to Adobe Support, they have people to support installation.

You can email techcomm@adobe.com or phone in whatever country you are in.

Thanks! I installed on WIndows 10 with admin rights. Here is the error when I tried to start the 30 day trial.

Did you install with admin rights? To the default location? Which version of Windows?

What exactly are you doing, just opening the application or trying to open a project?

What is the full error message? Can you post a screenshot? (I realise the error may be super unhelpful, but it doesn't hurt to get the exact text, just in case.)