The version of Form you have installed is very old, version 1.0.2 was released about 3 1/2 years ago and has not been compatible with WordPress for a couple years due a change they made to the Visual Editor included with WordPress. The current version is 2.4.3.
The version installed does not support in admin updates so you’ll have manually update. To do this
- Make a backup
- Download the current version from your purchase history
- Deactivate and delete the installed version.
- Install the current version.
After your update, the visual tab should work again.
Hope that helps, let me know.
ps. Make sure to activate your support license key so it can be updated right in admin like other plugins.