If you've received an email from Salesforce that is similar to the following then this article is for you!
We were unsuccessful in enabling the ICU locale formats release update in your production org. The enablement failed because this org contains one or more Apex classes, Apex triggers, or Visualforce pages that are using an API version less than 45.0. We will try to enforce this release update again in the next release.
At this time we ask you to review and update any Apex classes, Apex triggers, or Visualforce pages to API version 45 or higher. You can also choose to enable the ICU locale formats on your own.
Our team is actively working on updating all our packages to v45 or higher. In the interim please make sure you have the latest Soapbox Engage package(s) installed as some may already have the latest API versions updated (latest versions here).
Additionally, you can refer to this Salesforce help article which states the following:
JDK Locale Format Retirement and the Enable ICU Locale Formats Release Update
If your org contains lower API versions of these components, Salesforce won’t enable ICU locale formats in your org. Your org will remain on JDK until you manually enable ICU locale formats.
Please "follow" our Soapbox Updates page to be notified once a new package version is ready for you to install: Soapbox Engage and CMS Updates