Did you Update Anything!?
Unfortunately, while updating is a great way to keep your site secure and functioning properly, sometimes corrupted or wonky files are introduced when you update an item.
Because of this I would recommend ALWAYS backing up your site before you start updating things just in case something breaks (could be a lot worse than just missing your Wordpress visual editor).
When you first log in to your site everyday it is normally pretty good about making updates super obvious. If you want to double check though you can click on dashboard and then look at the update option. If updates are available there will normally be a number next to it telling you how many there. It will show all the updates available for Wordpress, your themes, and your plugins.
When you click on the updates it will take you to a page showing you everything you need to update. Once everything has been updated then you will get this lovely message from Wordpress when you go to this area.
If you have recently updated anything there is a chance you might have gotten a corrupted version of it. As mentioned previously, you can try deactivating your plugins one by one to see if it comes back or deactivate all of them and then reactive one by one. In the case of plugins you can delete and try reinstalling a good version. You can do the same for themes but you will lose any settings you had with it.
Normally in these cases I would simply contact support (premium members only) especially if the problem occurs right after you upgrade your Wordpress.
Yet again, want to emphasize backing up your site just in case (even though WA support is awesome)
Backup Training
Quick and easy method using tools export https://my.wealthyaffiliate.com/training/how-to-ba...
Backup to a Google Drive account https://my.wealthyaffiliate.com/training/how-to-ba...
Premium members - your site is backed up by the WA hosting servers for all your sites hosted here so if things go completely south they can normally restore it for you. Though you should still get in the habit =).
Still having visual editor problems!?
One last thing to do.