My existing provider says the number should transfer just fine.
If Republic’s number checker is failing your number, perhaps the following will provide context?
Republic, like all service providers, relies on a Local Exchange Carrier (LEC) to host phone numbers. LEC is telephone industry jargon for phone company. Republic uses Bandwidth.com, as its’ LEC. Bandwidth needs to have a “presence” in the rate center where the number you wish to transfer (port) is located. A rate center is a geographic area, usually but not always a city or town. The rate center your number is located in is determined by the area code and prefix (first six digits) of your phone number. No carrier has presence in every rate center. Bandwidth has presence in most but not all rate centers. Unfortunately, if Bandwidth does not have presence in your number’s rate center, you will not be able to bring it to Republic.
An analogy that might help make sense of this. I grew up in Massachusetts where Papa Gino’s is a popular place to get pizza. Now that I’m in Florida as much as I’d like to purchase a Papa Gino’s pizza, I’m unable to do so because they have no restaurants (presence) here.
Republic can offer you a new number, perhaps, in a nearby rate center.