Hello,

Because those sliders share the same ID, so only the first slider displays. You can follow one of the two solutions below:
Solution 1: In page admin/structure/md-slider, please clone slider. Then there is another block slider and you can assign to any region. Then, your sliders will have different ID and they can all be shown

Solution 2: Open file md_slider/assets/js/frontend/init-md-slider.js and replace:

$.each(drupalSettings.md_slider, function(slid, slider) {
                   listMegaSlide[i] = $('#md-slider-' + slid  + '-block').mdSlider(slider);
                   if(slider.device_enable){
                       cssInline += '@media (max-width: ' + slider.device_width + 'px) {\
                           #md-slider-' + slid + '-block .md-objects {\
                             display: none;\
                           }\
                         } ';
                   }
                   
                   if(slider.device_width){
                       cssInline += '@media (max-width: ' + slider.device_width + 'px) {\
                               .hideonmobile {\
                                 display: none !important;\
                               }\
                             }';
                   }
                   
                   i++;
               });

with:

$('.md-slide-items').each(function(){
                   var slid = $(this).attr('id').split('-')[2],
                       slider = drupalSettings.md_slider[slid];
                   listMegaSlide[i] = $(this).mdSlider(slider);
                   if(slider.device_enable){
                       cssInline += '@media (max-width: ' + slider.device_width + 'px) {\
                           #md-slider-' + slid + '-block .md-objects {\
                             display: none;\
                           }\
                         } ';
                   }
                   
                   if(slider.device_width){
                       cssInline += '@media (max-width: ' + slider.device_width + 'px) {\
                               .hideonmobile {\
                                 display: none !important;\
                               }\
                             }';
                   }
                   
                   i++;
               });

Hello,

Did you clear Drupal cache?

Please send us your site url and admin account to check this issue