Again, I wasn't trying to throw shade on your report
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However, just so you have realistic expectations, it's at least somewhat likely there's no bug here.
Let's say you have a 1 in 20 chance of getting a skill up (the exact number depends on the details of intelligence and the item's trivial). In 50 attempts, the odds that none of them will hit that 1 in 20 chance is about 7.7% (according to the AI I asked ... I never took statistics).
That's unlikely! But, if you think of how many combines you've done, it's not surprising that one batch might be extra bad. Now, 1 in 20 was a rough number, and maybe it's only (say) 1 in 15 ... but either way, the point is that regular old bad luck explains your situation ... and also explains why you got no trivial message.