Cppy and paste is stopped working in the excel spreadsheet

Dear Sir,
I've the problem to copy and paste the formula that has been written and used for some time. It stopped working due to unauthorised person edited the files, and I'm not sure what's function used. It caused the spreadsheet unable to copy and pasted by using the existing formula to new insert or current grey column. For instance, row 17 to 19. I've added the formula that can be copied to row 6 to 15, but now I can't do it anymore. I can insert a row at column 17 to 19 while at the same time copy and paste the formula, however, can't do the same thing from row 6 to 15.
Can you please advise me what is going wrong and tell me the solution for this problem.
Thank you.

Hi,

attempt: you could try to convert your table to a range of data and then try "copy and paste again".

The only column that contains formulae is A, and I had no problem copying the MONTH(date_col) formula from A6 to A15.
Please can you provide more detail explaining exactly what you are trying to copy and paste that isn't working?
Incidentally, looking at Name Manager, you seem to have quite a number of invalid entries that you might benefit from tidying up.