New Teams plays back videos with reduced volume when sharing a screen. Windows can reduce sound from all other programs during communication by 80% as default.
Solution: Reset the default sound adjustment by following the numbered items shown in the picture below (this is for Windows 11).
Use the task bar to search "Settings" >> Choose System from the options on the left pane then select Sound >> scroll down to 1: - Advanced - More sound settings (Windows 10 calls this "Sound Control Panel") >> 2: Select Communications Tab >> 3: Select "Do nothing" radio button.