fix

app/code/Magento/Swatches/view/frontend/templates/product/view/renderer.phtml

@@ -7,7 +7,19 @@
 <?php
 /** @var $block \Magento\Swatches\Block\Product\Renderer\Configurable */
 /** @var \Magento\Swatches\ViewModel\Product\Renderer\Configurable $configurableViewModel */
-$configurableViewModel = $block->getConfigurableViewModel()
+$configurableViewModel = $block->getConfigurableViewModel();
+
+
+$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
+$chartBlock = $objectManager->get(\Magepow\Sizechart\Block\Product\Sizechart::class);
+$sizeChart = $chartBlock->getSizeChart();
+$chartTableArray = [];
+if ($sizeChart != null) {
+    $chartTable      = $sizeChart->getData('custom_size');
+    $chartTableArray = $chartTable;
+}
+$chartTableArray = json_encode($chartTableArray, true);
+
 ?>
 <div class="swatch-opt" data-role="swatch-options"></div>
 
@@ -21,7 +33,7 @@ $configurableViewModel = $block->getConfigurableViewModel()
                 "gallerySwitchStrategy": "<?= $block->escapeJs($block->getVar('gallery_switch_strategy', 'Magento_ConfigurableProduct')) ?: 'replace'; ?>",
                 "jsonSwatchImageSizeConfig": <?= /* @noEscape */ $block->getJsonSwatchSizeConfig() ?>,
                 "showTooltip": <?= $block->escapeJs($configurableViewModel->getShowSwatchTooltip()) ?>,
-                "sizeChartData": <?= \Magepow\Sizechart\Block\Product\Sizechart::getChartJson() ?>
+                "sizeChartData": <?= $chartTableArray ?>
             }
         },
         "*" : {