Well the truth up to a point. No one will want to hire folk who doesn't pay much attention to their training. Say your training is out of date and unused for ages, don't say you aren't good at listening to instructions.
Certificates can be lost, or in my case recently, slung out by persons unknown because the company didn't give enough locker space to store everything so I had a pile of important papers under my desk because there was no better solution.
Meanwhile you could re-read the leaflets you had, and maybe refresh your memory at trusted websites.