The only time I had sync problems was when I was connected to a VPN. Do you use one by chance?
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no, i have never used one mroe than once a couple of years ago
I had this same problem for months and had a hard time finding anything on it. The thing that finally fixed it for me was to disable IPv6 on my network adapter. After that everything syncs fine.
I applaud you coming here, but you might have better luck on the steam forums as there are more people there who might have the same problem
the steam forums are a horrid mess to sif through
but i was able to find some similar people and all they got suggested was retrying until it works or enable and disable syncing altogether, neither unfortunately worked