If you are getting notifications from SiennaEssentials, then your Mac is infected with adware. SiennaEssentials is adware for Mac.
SiennaEssentials changes setting in your Mac. First, SiennaEssentials installs a browser extension in your browser. Then, after SiennaEssentials hijacks your browser, it modifies settings in the browser. For example, it changes the default home page, modifies search results, and displays unwanted pop-ups in your browser.