The TV manual doesn't show any volume controls on the TV. I assume that you can't get the remote to change the volume.
The remote seems to be only for the TV so there might not be a reset. You can try removing the batteries and looking in the battery compartment for a small hole with metal showing. A reset would look like that. Leave the batteries out for a half hour and put them back. You may have another remote that has the volume codes for your TV. Otherwise maybe you need to buy a replacement original or a universal remote.