In my experience this is a common enough phenomenon. Happened to me twice here. All kinds of sites employ “professional” services that keep them “safe” by letting them know when someone uses the service from a Tor address, or plain blocking such surfers. The problem is that these “professionals” simply read the Tor consensus and ignore the (non) existence the Exit flag in the nodes. So someone who runs a relay node from his home can be reported as “using Tor” because his home IP address is listed as running a node, even though his node does not have Exit flag.
Last time this happened to me it was with an online shop and the message I got on the screen an email address of the “security” service which I should contact to clarify the issue. Instead of doing so I used the domain name of the email address to identify the company, and then wrote to the online shop that their ‘security” service provider is ruining their business by blocking and scaring away their online customers, falsely claiming that they use Tor. Half an hour I could access the site without a problem.