.
Okay.
So it looks like your STB's Model Number is MCM3000
Have you connected your STB to the Internet using LAN Cable or Wi-Fi?
If you had not connected your STB to the Jio Modem using LAN cable even once since you bought it, that could be a possible reason for the STB still being on the 2018 (you had mentioned in your earlier comment that it was still in Dec 2017 patch. I am going off of your screen shot though, as it shows that the security patch is Dec 2018) security patch.
So let us try this, even if you had connected it using LAN cable before. If you don't have it connected to the Jio Modem using a LAN cable right now, please give that a try.
Connect it using LAN cable and leave it alone for a couple of hours. Then restart the STB using the option from settings:
Settings --> About --> Restart
If at all there is an OTA Update for your STB model number, it should receive it through direct connection using LAN (for the first time ever).
If nothing happens even after a couple of hours, then we can safely assume that the 2018 Security Patch is the latest available patch for your STB model.
P.S:
1) I realize only now, that your STB's model number is actually mentioned in the Version field of the UI screen shot that you first shared. It says MCM3000-4.16
2) In fact, I am also realizing that even though the Security Patch Level is dated Dec 2018, the actual Build Date of the STB itself is dated January 2020. Notice the date in the Version & Build field from your UI sceeen shot. It says, 202001271133, which is Jan 27, 2020, immediately followed by probably the Build Number, which is 1133.
3) So, unless there is another Build for your STB model in 2020, I don't think you would receive another OTA Update.
4) Let us give the LAN cable thing a try anyway (unless you always have it connected using a LAN cable. you should be all set in that case
)