the whole solution is here
Experts at https://ecomitize.com/ recommend following these instructions:
Delete the generated / code directory rm -rf generated / codeThen runphp bin / magento setup: upgradephp bin / magento setup: di: compilephp bin / magento cache: flushchmo -R 0777 var / pub / generated /
Hopefully it helps.
Worked flawlessly. Thank you!