I have updated to v4.5.29 and v5.0.47-C38 and I have tried the migration again. I now get the following error.
v5
[2021-01-14 10:56:36] production.INFO: Importing invoices
[2021-01-14 10:56:36] production.INFO: Missing resource key: client_contacts_5
[2021-01-14 10:56:37] production.ERROR: Missing resource key: client_contacts_5 {"userId":1,"exception":"[object] (Exception(code: 0): Missing resource key: client_contacts_5 at /var/www/invoiceninja/app/Jobs/Util/Import.php:1324)
[stacktrace]
v4
[2020-09-14 20:09:55] production.ERROR: ***InvalidArgumentException*** [0] : /var/www/html/invoiceninja/vendor/laravel/framework/src/Illuminate/Support/Manager.php [Line 91] => Driver [.env] not supported. {"context":"PHP","user_id":0,"account_id":0,"user_name":"","method":"GET","user_agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:79.0) Gecko/20100101 Firefox/79.0","locale":"en","ip":"185.234.218.42","count":1,"is_console":"no","is_api":"no","db_server":"mysql","url":"auth/.env"} []