Highcharts Ordinal Issue - json

Question

I am struggling to understand why I cannot get the ordinal aspect of my spline type chart to work correctly! I created a series of bar charts a long time ago but having not done anything like this in years I'm a tad clueless and needing some guidance, I've spent hours trying different methods and nothing works wether using Highcharts or highstock.
The code I have in the head of my page is as follows:
$(document).ready(function() {
var options = {
chart: {
renderTo: 'container',
plotBackgroundColor: null,
plotBorderWidth: null,
plotShadow: false,
type: 'spline'
},
title: {
text: theTitle,
x: -20
},
xAxis: {
ordinal: false,
type:'datetime',
labels: {formatter: function() {return Highcharts.dateFormat('%b %e (%y)', this.value);}}
},
series: []
}
$.getJSON("data_weight_loss.php", function(json) {
options.xAxis.categories = json[0]['data'];
options.series[0] = json[1];
chart = new Highcharts.Chart(options);
});
});
The dates are in datestamp format in my MySQL database as "2022-06-28 09:02:45" and despite trying all sorts I'm confused to how I can get the dates in my chart to add the dates in that don't already exist?
This image shows the chart on how it currently looks but has no relevance as the dates that are missing means the chart is not very helpful. It's been a long time since I used Highcharts and even did anything like this but as a personal project I'd love to get my chart working with the ordinal aspect in place. Is there anything glaringly obvious that I have done wrong?
The data for instance is like this if I look directly in the data call from the php page.
[{"name":"Date","data":[1651695362000,1652140800000,1652227200000,1652313600000,1652400000000,1652918400000,1653264000000,1654214400000,1654473600000,1654560000000,1654819200000,1655164800000,1655251200000,1655424000000,1655683200000,1656288000000]},{"name":"Weight","data":[2188,2000,1986,1962,1948,1868,1834,1744,1728,1720,1702,1682,1676,1666,1652,1622]}]
Any help would be appreciated, thank you.