I selected Tools, Options, Tool Locations and my project was set to Auto Select Editor. I switched it to "used default editor" and ensured the project is default is set to Robohelp WYSIWYG. I found another person having a similar problem. I am able to open my topics in Robohelp 7 now, but it is still putting the .htm extension on my topics in the Project Manager. This install is on Windows 7 on my local hard drive. I am the only person using the software. My copy of Robohelp 7 is an upgrade from a full verison of Robohelp 5X.
Glad you sorted it as I was just about to post those steps.
For the HTM files, try clicking View > By Topic Title.
Helpful and Handy Links
Thanks Rick. I just found that options. I am not sure how it got changed. I might have done it by accident when I was searching for a fix with the opening topic problem.