There are a few things that might be the problem. First, when I pasted your code in, I noticed that there was a syntax error. There’s a period after QueryRequest() and there’s another period right after it before Statement.
Second, in your N1QL, there’s a comma after $modifiedTimestamp, but following that is a WHERE clause. This is a syntax error.
Third, do you have appropriate indexes created for this kind of query?
Fourth, in your code, I don’t see that you actually execute the query. Something like bucket.Query<dynamic>(queryRequest).
And finally, I agree with @vsr1 that you should execute the query in Query Workbench to make sure it’s actually doing what you expect. In your query, you use both meta().id and documentType in the WHERE clause. If the document doesn’t have that documentType property or the key is incorrect, then the query will be “successful” but it won’t actually do anything.
For more help, you can check out the documentation on using N1QL from an SDK here: https://docs.couchbase.com/dotnet-sdk/2.6/n1ql-queries-with-sdk.html