Sudden duplicate contacts

Why have I suddenly got duplicates to all my contacts and deduplicating them doesn’t work at all. Please explain I would appreciate thankyou

Do you have more than one account in eM client, in which those accounts share some of the same contacts?

As far as I know, I only have one account in eM Client. I did reinstall at one point but that was a long time ago. I just noticed this a few weeks ago because I very rarely go and look at my contacts list, but I searched for someone and noticed that there were two entries and then checked it out and realized that most of my email addresses were duplicated. I went and tried the deduplication, but it did nothing at all so I have contacted you as to why? I checked my accts and I think I only have one because my address has not changed in the last 10 years