OPOS Driver not open or locked by another application

I am getting above error when I try to print receipts. I have TM-T88IV with usb connection. it was working fine until I installed new regular printer (full page!) with usb connection. Now I have uninstalled this new printer, restarted, deleted Opos printer and added it back... no luck, I get the above message. another funny thing is somemtimes, it takes few seconds as if its printing something, but doesn't show the above message or doesn't print the recceipt either.... HELP PLEASEEEEEE