I tried to file my 2017 taxes and it was rejected because it says I was claimed by another person. How can I get my taxes filed?

The ONLY way to file your 2017 tax return is to print it, sign it and mail it. A 2017 return cannot be e-filed now. If someone else claimed you as a dependent and you claim yourself, the IRS will process your mailed return and eventually will contact both you and whoever claimed you to sort it out.

Also— did you use the 2017 software for your 2017 return? The current online software is only for a 2018 return. Using the online software for 2017 income would be a big mistake.