OK, things are considerably clearer now.
1. Assuming your Toshiba laptop's 2 TB SSD boot drive (don't call it a "primary drive" - refer to it as your *boot* drive - the partitions you set up on a HDD or SSD are all (or nearly all) "primary") was MBR-partitioned (as appears the case), when the contents of the boot drive were cloned to the 4 TB SSD (which had replaced the current secondary SSD) the resultant partitioning scheme on that 4 TB SSD was also MBR, REGARDLESS OF THE FACT THAT IT HAD BEEN FORMATTED GPT PRIOR TO THE DISK-CLONING OPERATION. THE CLONING WOULD OVERRIDE THE ORIGINAL FORMATTING.
2. Since only 2 TB of that MBR-partitioned 4 TB disk could be recognized by the system the resulting 2 TB of disk-space would be unallocated & unusable while the disk was MBR-partitioned.
3. Now you transferred (copied or moved) some additional files onto the 4 TB drive and apparently something went awry with that operation. It's impossible to tell what from this distance.
4. In any event you now recognized the 4 TB SSD was MBR-partitioned since only 2 TB would be detected by the system in terms of usability.
5. Now it is possible that the 4 TB SSD can be converted from MBR to GPT so you can utilize its full disk-space. Unfortunately you cannot achieve this using Disk Management without the loss of data. But you can use a third-party partition management program, e.g., AOMEI, Easeus, Mini-Tool, Partition Manager to carry out this operation without the loss of data. I believe their free or trial versions have this capability. I know their commercial versions do. The conversion process USUALLY works without a problem when the disk contains non-OS files. If the disk contains an OS (even if it not the current boot drive) the program may balk at carrying out the conversion process. So keep that in mind. And it's a good idea to copy or clone the data on the drive before undertaking this conversion process (unless, of course the data exists on other drives).