As per design, you can convert only a MSP requester to a technician. To convert a MSP Requester to a Technician do the following steps:
1. Login as Technician who is having SD-Admin role.
2. Click “MSP Requester” present under “MSP Details”.
3. Drill down into the requester and click “Change as Technician”
4. Associate the accounts / sites / Roles for the technician.
5. Save the configuration.
Now the mentioned MSP requester will be converted into a Technician.