P: I can't export a file into a GIF

[FeedbackCommunityMember]

So, I have this PSD file with animation in a timeline, I was able to render as a video, but not as GIF, not in Save for Web, Quick Export GIF or even Export As. In all of that options the program exports the static frame selected at the moment. When using the Save for Web, even in the preview mode, the GIF does not move, it is there, still. But the rendered video and the playback at timeline work smoothly.
I know I'm in a really old machine, a MacBook Pro Mid 2009, with El Capitan 10.11.6 and using the Photoshop CC 19.1.9, BUT I have a similar file that is working just fine.
Someone has a light to give me on this?

[c.pfaffenbichler]

Can you provide the file or at least post a screenshot including all the pertinent Panels? 
What are the image’s pixel dimensions, bit depth, number of frames, ...? 

[FeedbackCommunityMember]

Of course, I'll post two screenshots, the first with the animation going in the timeline, the second with the GIF hard still in the exporting window of Save for Web. And here a link to the file I'm working on.
https://drive.google.com/file/d/1hs30bRTT58KtvJ9JB7rdB7r0roY9LBcg/view?usp=sharing

Image is 900x1200 px, I'm trying to export the first 108 frames

[FeedbackCommunityMember]

[FeedbackCommunityMember]

I forgot to answer one of your questions, it was in 8 bit. But when I looked it up to answer you, I saw the color mode was in Duotone, so I changed to Grayscale and then was able to export. Never thought that would be the problem, but aparently its solved now. Thank you!

[J453]

Yep. That's what I found too. RGB works, too.

[c.pfaffenbichler]

I guess one might even say that for animation RGB is the generally preferred color mode.  (edited)