Can't choose content type anymore
This is caused by a hiccup in the node menu rebuild after installing a new module. If you run into this issue, its likely due to one of three problems, which you can address in the following order:


Clear full cache, forcing the content menu to rebuild
Go to the menu options under /admin/structure/menu/manage/navigation and look for your add content menu items and make sure they are disabled
If these two fail, then there is probably an error in your build that is preventing the menu from rebuilding correctly - check in your error logs for any issue there and address.