Audacity is already running

I had six open Audacity files and exported all of them as MP3s. Audacity then crashed and I re-opened it and discarded the last session. I then shut it down but have been able to open it ever since due to this message:

Audacity is already running.

The system has detected that another copy of Audacity is running. Running two copies of Audacity simultaneously may cause data loss or cause your system to crash.

Use the New or Open commands in the currently running Audacity process to open multiple projects simultaneously.

I deleted and reinstalled Audacity thinking that might solve the problem but it has not. The online information says this error only happens on Macs but I am running Windows 10 and have no idea how to get Audacity working again. Any help would be much appreciated.

Try rebooting your computer. Does that fix it?

Also, the current version of Audacity is 2.4.2 and is available via the Audacity website:

Use the Ctrl + Shift + Esc Keyboard Shortcut to get direct access to the Windows Task Manager.
You should be able to locate any Audacity process running in the background. Right-click on it, and end the process.