1. Disable One Step Checkout module and test the default checkout.
To disable the module please go to Admin Panel > Amasty > One Step Checkout > Configuration
Alternatively, run the following CLI command:
php bin/magento module:disable module_name
If the issue persists with our module disabled, it’s related to the default checkout, not our module. (Please keep in mind that Amasty One Step Checkout is heavily dependent on the default checkout. Once the issue with the native checkout is resolved, Amasty OSC should function properly as well).
2. Check for other third-party checkout modules.
Verify whether any other checkout extensions from third-party vendors are installed. Please note, two checkout modules cannot coexist on the same instance. If more than one checkout is installed, please disable all others except Amasty OSC.
3. Verify module versions.
Confirm that the main module and all sub-modules are up-to-date: How can I check the current version of my Amasty extension?
If any modules are outdated, please update them: How to update an Amasty extension?
4. If you’re using a Hyvä theme.
Ensure that all Hyvä compatibility packages are installed and updated. Kindly check the following article: One Step Checkout does not appear on Hyva theme. What should I do?
5. If experiencing infinite loading, missing blocks, or a blank checkout page, you can try disabling the following settings:
Enable JavaScript and HTML bundling and minifying for checkout page.