The only logical conclusion is that you downloaded a trial version in the past and are now being blocked from downloading it again. Is that possible? If you did download in the past - for what version was this?
I would definitely suggest contacting tech support, but before you do - try rebooting your computer and downloading again. If the same thing happens and you haven't downloaded the trial - definitely be in touch with tech support. If you downloaded a trial version already, you'll need to use a different machine.
Sorry to hear that you are facing the issue while downloading RH 2017 trial.
Can you try to download RH 2017 trial from the below link?
You may try the different browser if you still get the same issue as you mentioned above.
Alternatively, you can also download RH 2017 using the below direct links.
In order to download Adobe RoboHelp 2017 Release, Please browse to the below URL :-
Step 2:- It will redirect to Creative Suite CS5 download page. Do not click on download. Kindly stay on that page and click the
below links one by one and save the files (Make sure you have the above link open in your browser before clicking the below two links)
When both the files finish downloading, then run the second file (.exe) and it will automatically extract the files from .7z file which will start installing Adobe RoboHelp 2017 Release on your computer.
If you are trying to download any previous version of RoboHelp then you can download it using the below link:
Let me know if you face any issues.
I have followed your suggestions and made it!
Thanks for your support