Theme doesn't load

[Sempervivum]

Very nice theme! Unfortunately it doesn't load for me. I'm using this code:

    breezePath = scriptPath + r'\Breeze\breeze.tcl'
    # the following line throws a TCL error:
    root.tk.call("source", breezePath)

    # Sunvalley is loading fine:
    sunValleyPath = scriptPath + r'\Sunvalley\sun-valley.tcl'
    root.tk.call("source", sunValleyPath)

    s = ttk.Style()
    print(s.theme_names())
    ttk.Style(root).theme_use('sun-valley-light')

I'm using Python 3.10