Yes, EAs and indicators for forex trading do work. The fact is, they're just tools. And, like with any instrument, the outcome is determined by what it is used for and how well it is utilised.
Indicators and EAs are based on live price actions (by applying mathematical calculations to the price actions). However, because EAs are bots, they lack the ability to think and evaluate in the same way that people do.
As a result, you should not trust these tools blindly.