Why a score without a job is a weak signal
A generic resume score can catch typos, missing sections and long paragraphs. It cannot tell you whether you look qualified for a specific role, because qualification depends on what that employer asked for.
Two resumes can score the same on a template check and fit the same job very differently. One might show the three tools the posting names; the other might describe the same work in different words that a recruiter's search will never hit. Checking against the posting turns a vague grade into a list of specific gaps.
If you are applying to several jobs, run a check for each. One analysis is one resume against one posting, and the free account covers 3 a month. Reopening a report does not use another one.
If your file is the problem rather than your wording, the ATS resume checker page explains the parse checks in more detail. If you write "CV" rather than "resume", the CV checker runs the same analysis with UK and European conventions in mind.