Garmin marq athele update failed

Please help 

oxymeter dosent work 

say mismatch update software

Sounds like a botched beta update.  Go back to the 15.73 webpage and download the zip file again.  Unzip and then copy each file into their respective folder on the watch.  Garmin's directions below:

www8.garmin.com/support/download_details.jsp?id=15220 

1. Download and unzip MARQ_***Beta.zip.
2. Place the gupdate.gcd file, found in the System_v*** folder, into the \GARMIN folder of the device.
3. If there is a Sensor Hub_v*** folder, place the gupXXXX.gcd file into the \GARMIN\REMOTESW folder of the device. Please note, not all Beta releases will include an update.
4. If there is a GPS_v*** folder, place the gupXXXX.gcd (or 006B310700.GCD) file into the \GARMIN\REMOTESW folder of the device. Please note, not all Beta releases will include an update.
5. If there is a ANT_BLE_BT_V*** folder, place the gupXXXX.gcd file into the \GARMIN\REMOTESW folder of the device. Please note, not all Beta releases will include an update.
6. Disconnect from your computer and proceed through the update.
7. If you would like to revert to the last public release software, drop the gupdate.gcd file found in the System_Backdate_v*** folder in the \GARMIN directory NOTE: If you revert to an older version of software, all of your settings will be reset to defaults.

OR... you can try plugging your watch into a PC with a USB cable and run Garmin Express.  Hopefully this helps!

Is this an APAC device? 

How to know?

In what country did you buy it? The versions sold in Asian-Pacific countries have different software and are not compatible with the software versions listed here. If you tried to load 15.73 on an APAC device that would certainly foul it up. 

It’s a second hand , i dont know the country of buying

assuming it’s an apac what could i do ?

I opened the garmin device xml and in description it say garmin marq , no mention of apac

Did you try a soft (or better hard) reset?! This would be the first I would try to do ...