I can no longer use Shift-F6 to rename, that keyboard shortcut does nothing now

I can still rename variables via the menu (right click-> Refactor -> Rename). I have recently noticed this, perhaps as a result of the latest 2019.2 update?

Can anyone suggest what I can try to fix this and regain the ability to rename using this keyboard shortcut?

This is on Ubuntu 18.04 on a Dell XPS 15. PyCharm info below:

PyCharm 2019.2 (Community Edition)
Build #PC-192.5728.105, built on July 23, 2019
Runtime version: 11.0.3+12-b304.10 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 4.18.0-25-generic
GC: ParNew, ConcurrentMarkSweep
Memory: 1894M
Cores: 12
Registry:
Non-Bundled Plugins: DBN, com.jetbrains.plugins.ini4idea, net.seesharpsoft.intellij.plugins.csv, org.intellij.plugins.markdown, BashSupport, Docker, org.toml.lang

Thanks in advance for any suggestions or comments.