The attendance feature adds a roll call assignment that shows up in the gradebook. You can put it in an assignment group worth 0%, and put everything else in groups that total 100%, if you do not already use assignment groups to weight grades. That assignment will calculate a percentage attendance, late arrivals will count as the percent you assign to it in the attendance settings. That total might replace the need for a report, depending on your requirements.
You can always dial back through the attendance days to update any days/students you missed. I find that it is easy to mistakenly enter attendance I collected on paper into the day of whichever day I update canvas, for example. We also have late additions to our courses during drop/add and those students have no attendance record for the day(s) before they were enrolled. You could go back and mark them absent, but it will lower their attendance percentage for days that were not relevant.
If you entered everything correctly, and it simply is not exporting the way you entered it, you can edit csv files in excel. If it shows something different in the excel sheet than you can see on the attendance tab, definitely ask canvas support for help finding out why. If it was from changes you just made, give it a day or two and try again, to see if there are any changes. We do not use quarters to divide a course at my school, so the settings that make those divisions might be impacting your results in ways I cannot predict. You might ask your canvas admin if there is any setting that might be interfering with your report.
