Something is blocking write access to the drive. Most likely some third party software which is mistakenly trying to protect the drive.
You don't happen to have any software running that's used to allow access to Mac formatted disks such as MacDrive do you?
Perhaps you should try initializing the drive in Windows disk management instead of using that EaseUs software.
Most generally any disk smaller then 2tb should be mbr.
There is no reason whatsoever to favor MBR over GPT unless you need the drive to work in a legacy environment such as Windows 98 or XP. But even then it'll still work because Windows will create the redundant MBR (though I'm not sure about Easeus).
GPT vs MBR has nothing to do with drive size other than the fact that MBR can't create a single partition bigger than 2.2Tb. MBR is an older format that was limited to only 4 partition entries. GPT is the newer standard and allows up to 128 partitions. However if you create the partition table with Windows it'll still create a legacy MBR partition table and insert the first 4 partitions.