Dear Harsh K,
That sounds something erratic behaviour of system as you are not able to see your company code in OAMK despite relevant GL is marked as "Asset Recon".
Try out this in system make a balance to "Zero" for said GL account and go to FS00 and remove "Asset Recon" and save. Hope this helps you. Once you do this, carry out with intended "GR Reversals"
Hope this helps to your issue, let us know if you need any more help.
Regards,
Pankaj Bhalerao.