It's probably not coming from the plugin directly, but from how the plugin has been implemented...
Without being able to see your code, the only thing I can suggest is going back and reviewing the documentation, and double-checking your code to make sure that you have properly set up everything.
https://experienceleague.adobe.com/docs/analytics/implementation/vars/plugins/getpercentpageviewed.html?lang=en
Where have you added this code to your Launch?
Remember that s objects and also the extensions aren't available in Data Elements... did you add the code directly into to your custom code block in your extension? Within the doPlugins area?
s.usePlugins = true;
function s_doPlugins(s) {
// code here
}
/******************************************* BEGIN CODE TO DEPLOY *******************************************/
/* Adobe Consulting Plugin: getPercentPageViewed v5.1 */
function getPercentPageViewed(pid,ch){var e=pid,i=ch;if("-v"===e)return{plugin:"getPercentPageViewed",version:"5.1"};var t=function(){if(void 0!==window.s_c_il){for(var e,i=0;i<window.s_c_il.length;i++)if((e=window.s_c_il[i])._c&&"s_c"===e._c)return e}}();function o(){if(window.ppvID){var e=Math.max(Math.max(document.body.scrollHeight,document.documentElement.scrollHeight),Math.max(document.body.offsetHeight,document.documentElement.offsetHeight),Math.max(document.body.clientHeight,document.documentElement.clientHeight)),i=window.innerHeight||document.documentElement.clientHeight||document.body.clientHeight,t=(window.pageYOffset||window.document.documentElement.scrollTop||window.document.body.scrollTop)+i,o=Math.min(Math.round(t/e*100),100),n=Math.floor(e/i),p=Math.floor(t/i),s="";if(!window.cookieRead("s_tp")||decodeURIComponent(window.cookieRead("s_ppv").split(",")[0])!==window.ppvID||window.p_fo(window.ppvID)||!0==window.ppvChange&&window.cookieRead("s_tp")&&e!=window.cookieRead("s_tp")){if((decodeURIComponent(window.cookieRead("s_ppv").split(",")[0])!==window.ppvID||window.p_fo(window.ppvID+"1"))&&window.cookieWrite("s_ips",t),window.cookieRead("s_tp")&&decodeURIComponent(window.cookieRead("s_ppv").split(",")[0])===window.ppvID){window.cookieRead("s_tp");var a=window.cookieRead("s_ppv"),c=a.indexOf(",")>-1?a.split(","):[],d=c[0]?c[0]:"",r=window.cookieRead("s_ips"),l=c[3]?c[3]:"";s=d+","+Math.round(r/e*100)+","+Math.round(l/e*100)+","+o+","+l+","+n+","+p}window.cookieWrite("s_tp",e)}else s=window.cookieRead("s_ppv");var v=s&&s.indexOf(",")>-1?s.split(",",7):[],f=v.length>0?v[0]:encodeURIComponent(window.ppvID),$=v.length>1?parseInt(v[1]):o,h=v.length>2?parseInt(v[2]):o,u=v.length>4?parseInt(v[4]):t,k=v.length>5?parseInt(v[5]):n,m=v.length>6?parseInt(v[6]):p;o>0&&(s=f+","+$+","+(o>h?o:h)+","+o+","+(t>u?t:u)+","+(n>k?n:k)+","+(p>m?p:m)),window.cookieWrite("s_ppv",s)}}void 0!==t&&(t.contextData.getPercentPageViewed="5.1"),window.pageName=void 0!==t&&t.pageName||"",window.cookieWrite=window.cookieWrite||function(e,i,t){if("string"==typeof e){if(g=function(){var e=window.location.hostname,i=window.location.hostname.split(".").length-1;if(e&&!/^[0-9.]+$/.test(e)){i=2<i?i:2;var t=e.lastIndexOf(".");if(0<=t){for(;0<=t&&1<i;)t=e.lastIndexOf(".",t-1),i--;t=0<t?e.substring(t):e}}return t}(),i=void 0!==i?""+i:"",t||""===i){if(""===i&&(t=-60),"number"==typeof t){var o=new Date;o.setTime(o.getTime()+6e4*t)}else o=t}return!!e&&(document.cookie=encodeURIComponent(e)+"="+encodeURIComponent(i)+"; path=/;"+(t?" expires="+o.toUTCString()+";":"")+(g?" domain="+g+";":""),void 0!==window.cookieRead)&&window.cookieRead(e)===i}},window.cookieRead=window.cookieRead||function(e){if("string"!=typeof e)return"";e=encodeURIComponent(e);var i=" "+document.cookie,t=i.indexOf(" "+e+"="),o=0>t?t:i.indexOf(";",t);return(e=0>t?"":decodeURIComponent(i.substring(t+2+e.length,0>o?i.length:o)))?e:""},window.p_fo=window.p_fo||function(e){return window.__fo||(window.__fo={}),!window.__fo[e]&&(window.__fo[e]={},!0)};var n=window.cookieRead("s_ppv"),p=n.indexOf(",")>-1?n.split(","):[];p[0]=p.length>0?decodeURIComponent(p[0]):"",e=e||(window.pageName?window.pageName:document.location.href),void 0===i||!0==i?window.ppvChange=!0:window.ppvChange=!1,void 0!==t&&t.linkType&&"o"===t.linkType||(window.ppvID&&window.ppvID===e||(window.ppvID=e,window.cookieWrite("s_ppv",""),o()),window.p_fo("s_gppvLoad2")&&window.addEventListener&&(window.addEventListener("load",o,!1),window.addEventListener("click",o,!1),window.addEventListener("scroll",o,!1)),this._ppvPreviousPage=p[0]?p[0]:"",this._ppvInitialPercentViewed=p[1]?p[1]:"",this._ppvHighestPercentViewed=p[2]?p[2]:"",this._ppvFinalPercentViewed=p[3]?p[3]:"",this._ppvHighestPixelsSeen=p[4]?p[4]:"",this._ppvFoldsAvailable=p[5]?p[5]:"",this._ppvFoldsSeen=p[6]?p[6]:"")}
/******************************************** END CODE TO DEPLOY ********************************************/