After running as admin, attempt the SHSH request again.
Before troubleshooting locally, confirm whether the firmware you are targeting is still being signed by Apple. Websites like ipsw.me allow you to check signing status for your specific device and iOS version. If the firmware is unsigned, no tool can request valid SHSH blobs. In this case, the only solution is to request blobs for a still-signed version. How To Fix Error Unable To Request Shsh On 3utools When