Too Much Blank Space
Large amounts of blank space are the first things hiring managers are going to notice on your resume.
Having around 50% of the page or more of your resume blank is not recommended. This can not only cause parsing issues with an applicant tracking system (ATS) but it can also reflect poorly and come off as unprofessional to a potential employer.
If you are having trouble filling up a single page, think back to projects you have worked on. What kind of transferable skills can you highlight from them? Need help writing bullets for projects or entry-level positions not in an office? Read this!
If your resume has gone to two pages with most of the second-page blank, try focusing on key skills you want to highlight for an employer. Remove any extra fluff to try to get your resume to a single page.