Influence and affluence are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Influence is an noun. It means someone or something possessing power over others’ actions and/or viewpoints.
Affluence is a noun. It means possessing wealth and enjoying the comforts that go with it. If someone possesses affluence, they said to be affluent. [Affluenza is a portmanteau of Affluence and Influenza. This portmanteau was an observation that the pursuit of wealth, living above one’s means, was a big problem in US. It was rampant, much like a flu epidemic. ]
The following story uses both words correctly:
Alfonse wanted to get into politics. Unless a person already had an existing brand with tremendous influence, or came from considerable affluence, though, this was a hard field to break into and make waves.