Q: problem with installing win10 on mac el captain

There are two types of Recovery, Local and Internet. Local will fail over to Internet, if the local is not a viable option. Please see OS X: About OS X Recovery - Apple Support for details.

Please retry BCA, if Brigadier works.

Are you interrupting the installation procedure manually?

How far away is your closest Apple Store or an Apple Service center?

I am going to the local Apple Store tomorrow. Let me find out what they can do to assist. If you do not have a stable internet connection, you will run into many issues.

Your 2015 Mac supports directly booting from Windows 10 installer. Do you have an ISO of W10, or a USB installer?

Please keep a copy of the proper Brigadier download, we can try other options.

If this a 2015 model, you should have an OSXRESERVED partition. Did you delete any partitions manually?