Not all date fields are showing up in Timeline slicer option

SergeiBaklan  thank you Sergei - yes there were some text in the data fields. These came from trying to insert a default date when a vlookup did not find suitable result in the lookup table.

=IFNA(VLOOKUP([@[uniq_line_item]],saved_promise_date_hard[#All],2,FALSE),"1/1/1900")

the thing is if the item being looked exists in the look up table but there is no data ie blank then it returns the value as a date

but if the value looked up does not exist in the look up table then default value returned is text formatted of the default

My question would be how could write this better that the default value entered is a date and not text. I have also posted this as a separate question since I marked your response to my initial question as best response. Please provide your feedback there if possible

AAbdou 

Dear Abdelrahman thank you for responding to my post / query.

I tried refreshing all data connections, as well closing and reopening the workbook. Unfortunately it did not work.

The reason was because some date were in Text format. So even thought the fields / column was formatted but due to a few bad formatted data it was not pulling. 

I have given details of this in another post. If you could help me on addressing the root cause that would be greatly appreciated as well.

Thank you very much for your valuable insights and time.