e Liquid does not contain THC. I'm not sure how it showed up "not as THC but as Cannabis." When you test for something, you generally need some kind of marker. In the case of Cannabis, they use THC, unless things have drastically changed over the years. In any case, your employer is primarily looking to ensure you are not high on the job and able to perform your duties safely.
The only exception to this may be if you are using CBD liquid rather than normal e liquid (this is speculation as it's not something we use or sell).
This link will give you a bit more background on CBD products: https://www.thegrowthop.com/cannabis-culture/cbd-consumption-cause-me-to-fail-a-drug-test
If you are failing your drug test, you're going to need to look into what else is in your diet or perhaps even your surroundings. False positives, while they do happen are unlikely. If you have a good employer and this job is important to you, sit down with your boss. Explain the situation and your concerns. Request that a hair test is done over a urine test. If you really are drug free, as stated, this will allow you to be re-tested while putting the concerns of longevity to rest with your employer as hair tests can go back 6 months or more. You may even wish to bring your e liquid depending on your career. If they're a good company, I'd imagine it's much cheaper for them to investigate and properly asses the situation rather than end up slapped with a wrongful termination lawsuit.