Try the following in order from top to bottom:
- Reboot the computer: Click the start menu and click turn off computer. Then a window pops up, with 3 options. Choose restart. Your computer will go through the turn off steps, and after that, it will turn itself back on. This fixes some things, one is off sync drivers. Another is where your computer was out of RAM and needed a reboot.
- Uninstall then Reninstall the latest version of LibreOffice: Go to control panel, add and remove programs, and remove the version you have. This removes whatever files might have been missing or corrupted that might be causing the no icon. Then Reinstall the latest version of LibreOffice which should include misiing files if there were any, fix any corrupted files, and fix any bugs that were fixed in that version and below.
Another option: CCleaner. It is a free tool (there is an optional paid version, which is normal for a lot of free programs. A lot of free programs have a better version of it: CCcleaner is in that free version tools group) that lets you remove registry errors, start menu that were left over from uninstallations, empties the recycling bin, etc. If you do this, do it after you uninstall but before you reinstall so it can remove whatever registries, start menu, or other things were left from LibreOffice.
If none of these work, it’s most likely a bug. The above options normally fix most ,if not all, problems (usually uninstall then reinstall) except bugs, since those are inside the program and that’s not what the above can fix. Bugs are what the developers have to fix.