New Access Services-based apps and web databases are no longer able to be created in SharePoint online. They will need to be migrated to a private cloud, like Fpweb, or an on-premises SharePoint environment, by April 2018, because Microsoft is retiring the feature from Office 365.
Access Web Apps and Access Services will continue to be supported in all current versions of on-premises SharePoint servers for the remainder of the product lifecycle for SharePoint 2013/2016.
The best course of action is to move Office 365 Access Web Application solutions to a private cloud, like US Cloud, or a SharePoint 2016 on-premises installation. Use a snapshot backup to restore the app in its entirety. This will allow data forms to be restored, thereby circumventing any manual recoding endeavors.
Finding a reputable company like Fpweb to do the heavy lifting of a migration like this is worth considering as well.