Excel Worksheet is not displaying data and rows are changing to 409.5 height instead of th

Welcome to the forum.

This sounds similar to problems reported on this technet(MS) site: https://social.technet.microsoft.com...ge?forum=excel
Most of the posters reported they were working with files in Excel97-2003 format (.xls) and this was happening to them in Excel 2010.

Two solutions suggested there:
1.
- Open [Excel Options] dialog. ([File]-[Options])
- Select [Advanced] tab, turn on [Cut, copy and sort inserted objects with their parent cells] option. (In [Cut, copy and paste] section)
This will not resize rows that are currently set to 409.5 but may stop this happening in the future.
2.
Select the entire area you're working on, change the alignment from bottom (the default) to top.

I can't guarantee either of the methods will work, but probably worth trying.