Hey, sometimes import fails when file is big and it gets timeout. You can try with smaller file by removing some data and trying importing again. If it will work then size of file is an issue.
Other option can be multiple userlib libraries or what is less likely but maybe you are importing it (opening) more than once if you have more than 1 instance of app and run microflow on all instances.
Seems like some dependency is missing (Mx Model Reflection, Community Commons Function Library) or a security issue.
Did you follow all the steps from this link?
May Be create a new excel file copy paste the content into the new file and try.
If the issue is with 1 specific file then there is something wrong with that file.
you can do 1 thing: try making a new template from this file (the sheet where the data is present)
then import the same file and see the result.
1 more thing: try to make a new file from another machine and get it send to you. Then try the whole thing.