New to me MacBook Pro Retina 13-inch early 2015 locks me out

[pincrete]

I assume you tried starting up with all external drives and installers disconnected - just using the internal boot drive.

I have done, many times!

 

[Slydude]

I have emailed the previous owner (in the UK) asking if he knows the firmware password - as yet no reply.

I had plugged in the external drive and selected it as startup before rebooting, so that probably triggered the firmware lock - which I simply didn't know about, having never had anything with that facility before, most of my Macs have been older.

What you're describing could indeed trigger a firmware lock if one has been set. In this case, the age of the Mac probably isn't an issue. I don't remember when that feature was introduced but it was available on several older models,

 

[Rod]

The OP states in his first post,"The Macbook duly arrived and started up fine. As I wanted to install a new system, I set the start up to an external HDD, the password to blank and restarted with the USB external HDD connected."
The point is it did not start up in the introductory mode (Not Setup Wizard). The OP says,"it had been already set up" which I assume means that it had not been erased so still linked to the original owner's account. The OP further states he set the Startup Disk to his Bootable EHD so he was able to login.
Trying to startup a laptop owned by someone else with an external HD created by another party is most likely what triggered the lock, I think.

 

[pincrete]

The OP states in his first post,"The Macbook duly arrived and started up fine. As I wanted to install a new system, I set the start up to an external HDD, the password to blank and restarted with the USB external HDD connected."
The point is it did not start up in the introductory mode (Not Setup Wizard). The OP says,"it had been already set up" which I assume means that it had not been erased so still linked to the original owner's account. The OP further states he set the Startup Disk to his Bootable EHD so he was able to login.
Trying to startup a laptop owned by someone else with an external HD created by another party is most likely what triggered the lock, I think.

All correct, basically unless I can get the firmware password - or proof of original purchase (including serial number), I'm stuck.
For all intents and purposes, it's behaving -and will behave- as though I stole it!

 

[pincrete]

I don't remember when that feature was introduced but it was available on several older models,

Apparently

• (2006-2010) – The firmware password could be removed by removing the battery, one stick of ram, and resetting the PRAM 3 times.
• (2011-2017) Apple changed this when they soldered the memory to the logic board. The only way to remove the firmware password was to contact Apple.

But all but one of my Macs has been pre-2010, and none has had the firmware lock set.

 

[Slydude]

Thanks for that info. I knew that feature had been around for a while.

 

[Rod]

I think you will have to play on Apple's sympathy here. Get together what proof of purchase you have from the online purchase and ask for assistance. You may find the serial number on the body (underneath) and check online at Check if lost or stolen - Stolen Register to see if the device has been reported as stolen.
Really the seller is your best hope here, try to get in touch with them via the online sale site, I think you said it was ebay so the vendor will be registered with them, or you can place a complaint against them demanding contact for selling a faulty product. If they can't provide proof of ownership or user name and password you can at least cause them some grief. Not much help to you though I realise.

 

[ferrarr]

It may not be a Firmware lock.

If it boots up normally. can you do this?

What to do before you sell, give away, or trade in your Mac

If it can set it up as new, then you may be able to install El Capitan.

 

[pincrete]

I assume you tried starting up with all external drives and installers disconnected - just using the internal boot drive.

Yes. I'm 'locked out' whatever I do and the seller hasn't responded to any requesy for the firmware password.