It appears you are using the online version and the editor is not drawing properly. Sometimes certain images fail to load due to networking or caching issues but that doesn’t seem to be the case.
Here are some things you can try:
use Chrome if you are not already (most drawing problems occur because of differences in browsers and Chrome is the primary supported browser)
scroll down - while the buttons didn’t draw they are only shortcuts to get you to the given block sections. But you can also scroll down with a mouse wheel or trackpad or even by dragging the little scroll bar to the right (assuming that is visible)
stretch the “block drawer”. There also should be a little icon all the way to the bottom right of the blocks that looks like three vertical lines. If you click and drag it to the right it should stretch the “block drawer” which may cause the drawer to redraw the missing buttons.
Let us know if this helps and which browser you are using so we can look into the issue.