Hi Kate,
Please try the followings to check the result:
1.Open IE ->click gear on the upper right corner ->Internet Options ->Under security, select trusted sites -> click sites, make sure the followings sites are listed there (please replace contoso with your own tenant domain name):
https://contoso-files.sharepoint.com
https://contoso-myfiiles.sharepoint.com
https://contosso.sharepoint.com
2.Open IE ->Internet Opyions->Programs->Manage add-ons, scroll to SharePoint names, make sure they are all enabled. Then click OK and reatrt IE.
If the error persists, we want to confirm some information for investigation:
1.Generally the steps to import Excel spreadsheet to Excel can be the followings, which stage do you get the error?
a.On the site, go to Site Contents->Add an App->Import Spreadsheet.
b.Enter a list name and description, click Browse->Select the spreadsheet->Open->Import, it will open the spreadsheet in Excel.
c.Select the data range, then in the Import to Windows SharePoint Services list dialog box click Import, the spreadsheet will import into the list.
If you are not performing the steps above to import spreadsheet to SharePoint list, please clarify the steps and let us know when you get the error.
2.I notice you saved your data on your OneDrive, if you import a spreadsheet from your local computer, will it exhibits same error? Also, do you sync your OneDrive files to your local synced folder and then browse to synced folder to import the spreadsheet? if not, please clarify the steps how you import the data from OneDrive to SharePoint list.
3.Please share the spreadsheet with us via private message so that we can try to test it on our side.
4.A full screenshot of your Excel product information page from File tab->Account.
5.A screenshot of the error message.
Regards,
Joanne