DeletedAssets returning 0 items

I have retrieved a result via:

var nextRes = await client.SyncNextResult(syncUrl);

but DeletedAssets returns no assets.

nextRes.DeletedAssets.Any()

returns “false”

nextRes.DeletedAssets.Count()

returns 0

Can you advise what I could be doing wrong?
Thanks.

I found that because it filtered SyncInitial with SyncType.Asset all future calls using the token and SyncNextResult still applied this filter. I just had to remove the filter.