As I see in the screenshot provided above, you don't have the available forum. That's the reason you can't add a new topic.
Please navigate to Dashboard > Forums > Forums admin page click on "Add New" button, create a new Category, then the new forum, then you will be able to add a topic.
Also please note if a category (blue panels) does not have forums (grey panels) it will not be displayed on front-end. Each category should contain at least one forum.
More info can be found here: https://wpforo.com/docs/root/categories-and-forums/
Could you please create a new admin user and check again. If the forums there, please update the admin user permission in the Dashboard > Users > Your profile admin page.
Also please deactivate and activate the plugin then check if all tables are not there, click on [Solve Database Problems] button. The button is located in the Dashboard > Forums > Tools > Debug > Tables tab.