PH fails to optimise gifs ?

[SE-Syd2042]

hey has anyone had this problem ... when optimising animated gifs the new Photoshop CC18 just give an error note

[JJMack]

I do not normally open animated gif in Photoshop.  I open the PSD files I create the Animated gifs with.  However I just opened some animated gifs I create in Photoshop with CC 2018 without any problem. All frames are also image layers. The layers used to create the frames are not in the opened documents.