Data Validity List its getting deleted

Whenever I am adding validity in libre sheet automatically its getting deleted after closing the file and then everyday I need to add it again. I have customise my sheet added few shortcuts of my own. Is that the problem or what?

Your LibO version?
Did you use an alien file-type (.xls / .xlsx e.g.)?
Your OS / version?
I did not yet find a related bug report.
I did not experience the described behaviour ever.

Yes I used .xlsx.

There are lots of problems with alien file “formats” because they cannot acually just represent the “same” information in different ways. In fact they partly pertain to the structures and proceedings of different software concepts… This will mainly show when features like validation, conditional formatting, change tracking, or protection are used.
If possible at all, always stick to the native file formats.
Some relics may persist nonetheless if a document was converted.

Which one is the native format?

.odt, .ods, .odg, … and the respective templates: .ott …
See: OpenDocument - Wikipedia