Yes! If it is a formative assessment, the teacher can reopen it. If it is a benchmark an Admin in Mastery Connect has to reopen it. If you reopen the assessment for a student the initial data is gone and replaced by the new submission data.
https://community.canvaslms.com/t5/Mastery-Connect-Assessments/How-do-I-reopen-a-submitted-formative...
https://community.canvaslms.com/t5/Mastery-Connect-Assessments/How-do-I-reopen-a-benchmark-assessmen...
If you want to keep the initial attempt data you might consider using the quick reassess tool.
https://community.canvaslms.com/t5/Mastery-Connect-Blog/Introducing-the-Quick-Reassess-Feature/ba-p/...
