I got a dui over 20 years ago was .o8,paid fines took class gave dmv my certificate, they lost it now they want me to take class again,

Sorry to hear.  If you took the class back shortly after you were convicted of the DUI class and had your drivers license, it is strange that this would come up now.  On the other hand, if you took the class but did not get your diving privilege reinstated 20 years ago and DMV doesn't have any record of you completing the class, that is a problem. Most DUI program providers would not have records going back 20 years.  Unless you can find the certificate of completion, it will be a problem and you will most likely have to take the class over again if you want to get your driving privileges back. Unclear where you reside, but many DUI programs are now doing the classes on-line due to Covid-19.