Thanks! i was having this issue in my tablet.For those of you having the "Not Detecting Sim" issue or it keeps dropping calls, you need not worry. I have an easy fix for you.
1.Simply Download "Mobile Uncle Tools" from Play Store open it and select "engineer mode" then "Engineer MTK".
If you don't want to download Mobile Uncle Tools then go to Dialer and dial ( *#*#3646633#*#* ) to get into engineer mode.
2. Once in Engineer Mode, under Telephony. Select "Network Selecting"
3. You will see "Select Preferred Network Type" Choose "GSM Only"
4. That's it...for some reason it doesn't seem to read SIM Card properly when it's on "GSM/WCDMA" and "WCDMA"
Maybe it the type of sim you're using...if this doesn't work the please let me know with a reply.
NOTE: No need to flash phone or update firmware to do this. Also, this is for the Ainol AX1 Poseidon.
This update is avaliable via OTA update to the tablet? I can´t find it in the downloads section of ainol chinese webpage, in english section only have two tablets.