hard drive - Recovering data on an MBR partition converted to GPT

first time poster but I've been a long time reader! Here goes...

I've just converted a WD Green, 2TB HDD (data only) NTFS - using Minitool Partition Wizard 9.1 from MBR to GPT. Drive was about 67% full.

Using Windows 10. I have a UEFI GPT boot drive. The website specifically said this does not lose data! Using the convert mbr to gpt command only took a couple of seconds (should it have been a long process?)

It now shows up as Basic GPT - Unallocated - empty space.
Also no drive letter is assigned.

Its not a system disk so no activity should have over written any data yet.

Before I try to recover the partition, does anyone have any experience - should I:

1 - first convert the drive BACK to MBR then try and recover the data?

or

2 - Is it safer to stick with the GPT and attempt recovery from its current type?

or

3 - Assign a driveletter and reboot, maybe the system will then see the GPT?

Thanks for any help!
AP