There is a train of thought that paying incentives is not always a good thing. Amongst less affluent or educated respondents it may predispose them to feel that they need to give so-called “good” or “correct” answers which may bias your results. Alternatively you may attract respondents who are in it just for the reward. One approach could be to run the survey with no incentive with the option to offer one if responses are limited.
Designing the survey so as to assure respondents of the time commitment and privacy implications of completing the survey can also help to increase responses.