Can not be sure, but it looks like the same issue I had here:
Where the portal is actually taking the shards, it just isnt updating updating in your client until you let the portal close by moving away from it or going through a couple more portals then going back.
In my case I could tell it was actually taking the fuel because the amount of shards in my SS changed even though the amount in the portal appeared to not change (but actually had).
There have been multiple other similar reports that might be the same issue as well.
I had a bug a few weeks ago where I couldn’t add fuel to my 2x1 portal. For example, let’s say there were 642 shards in the open portal, and I had a stack of like 749… and when I tried to add fuel it just wouldn’t go. I just kept shifting the stacks around until it finally worked.