It's to do with the Excel format Recorder produces - it's so old that (the new version of) Excel sees it as some sort of security risk. You need to disable Excels flagging behaviour - I can't remember exactly, but here goes (I thought there was a post on the forums about it but can't find it)  - hopefully someone will correct me if I'm wrong.

Click File then Options, then Trust Center, then the Trust Center Settings button then File Block Settings. Untick the check box next to "Excel 2 Worksheets", then OK, and OK again. Close Excel and try opening the file - it should work.

If you try to save any changes though, you'll get an error ("cannot be saved in the current format") and be asked to save it as a new file (Excel can't/won't write to the old format), but you can just save over the current file.