The service failure drew further criticism regarding the overall execution and customer cost of the upgrade.
"This is just not good enough. No doubt the new app has cost us, the customer, a fortune.
We deserve better. You need to do much better.
Shockingly bad," posted another customer.
In response, railway officials temporarily extended access to the legacy software to give technical teams time to resolve the errors.
"We're sorry for the delay to anyone switching their ScotRail app today.
We are working with our technical teams to clear this as quickly as possible and we apologise for the inconvenience.
Customers who are having issues can continue to use the old ScotRail app to purchase tickets until midday," said ScotRail in a statement.
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Prior to the launch, ScotRail had instructed users to execute a password reset upon their first login and advised passengers to download existing tickets, which will remain accessible on the old app until it is retired later this year.
