Switch your bobbin thread would be the first thing to try.
If this is a new purchase go back you may have a defective item that should be taken care of. Since we deal in vintage amchines we quite often get calls of ension off etc. 9.5 percent of the time they have missed one of the threading guids or discs time and tme again and have set themselves up for trouble. We take great sympathy for them as we work on machines many times that have no manual and are just a hair different that another machine. Consut the manual,go on line and look up sewing machine trouble shooting or call the company.