Could be something in the spreadsheet. Could be the location of the file.
Could be just about anything. If that spreadsheet doesn't work and others do, and others don't, you need to put the does and don'ts into some common category that is the root problem.
On that note, check out the help tips in the link I sent, which I am sure you are aware of.. but there may be a glimmer you may have missed (hidden this, split that, links anything, etcetera... that foul spreadsheets allow are generally not in arc*world)
Also tomorrow morning a 7:00 AM, I am releasing a blog post on Excel use and data issues when working with it and ArcGIS Pro
If you must work with spreadsheets, the rules are strict. Anything that allows for mixed data types has even more rules.
Arrays of a uniform data type are best… then it doesn't matter what goes into the rows/columns/cells (ie images)
Arrays of mixed dtypes have to keep the rows or the columns of one data type, then you can stack them row-wise or column-wise as long as you know what is where and can define it (ie tables in general, like dbase, arc*whatever tables, numpy arrays etc, most other science-used data formats)
Spreadsheets don't have such rules. You can put anything anywhere. Maybe that is why everyone uses them.