1. For Prestashop 1.6, unless some very old themes, almost 1.6 theme you can download jmsslider_1.6_update.zip

if your module slider is very old version, it will has name folder is modules/jmssliderlayer, please download jmsslider_old_version_1.6_update.zip

2. For Prestashop 1.7, slider has 2 versions. Open modules/jmsslider folder, if you don't see ajax_sliderchoice.php, please download jmsslider_updated.zip, if you see ajax_sliderchoice.php, please download jmsslider_2_updated.zip

After downloading, backup current modules/jmsslider folder, please unzip file,  then copy overwrite to modules/jmsslider folder.

if you still have problem, please contact us for getting support

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