JBL Speaker volume control problem

Hi all, new poster,no too tech savvy and unsure of which section to post in. Just fired up our brand-new Dell Inspiron this morning, plugged in the battered but still very serviceable JBL M310 J2.1 surround speakers,and couldn't turn the volume up using the on-speaker controls. The right-hand desktop speaker has + and - buttons which increase/decrease volume and mute if you press both. I can decrease and mute but not increase.
Plugging them into our also new Asus laptop, also running Win 10, they play OK and I can increase and decrease vol. The only difference is when I use teh laptop I ge the fmiliar-to-me Realtek audio control page whereas the Dell PC I get the Dell audio control page.
Can anyone offer any suggestions please?

Click on the speaker icon bottom right and set the volume to 100%. Play some music. If it is still low, you may have to increase individual volume controls. Right-click on the volume icon and select mixer while playing the music. See if any volume is low and increase it. Also set the volume to max from Windows Media Player or whichever application you use. Next thing to try is to right-click on the volume, select Playback devices. Click on Speakers, then Properties. Then click the Levels tab to see all levels. Move the sliders to the max to see if there is any difference. Back in the Playback devices, click on Speakers and then Configure. Select Stereo, then click next. Check the box to set the speakers as full range (supporting all frequencies), click next and then finish. See if this makes any difference. Also unplug and re-plug the speakers, in case there is a bad contact affecting the volume.