While some providers are staying up to date on their email, not all of them can handle the amount of email they get (they get a fair amount of spam, and like most sales-types, are loath to delete/filter their email for fear of losing a potential sale).  Some have said they get hundreds of emails each day so it might take a day or two before they get back to you.

Sometimes, they even take a break for a few days and might let things go for a while.  Best thing is to be patient.

One corollary to the above is that you shouldn't expect a lot of banter via email.  Might be the norm where you're from but it ain't like that here.

One final thought, if your email had the wrong tone to it (asking the wrong types of questions or being explicit), it might have gone straight into the bit bucket.  Keep it short and sweet (I want an appointment, here's my name, time/date/length I want to do it, hotel I'm staying at, and a mobile number to get in touch with me when I get to town).  Some require some references and/or verification info.  At least you're planning in advance which is the right way to do it.

Bob