Please review the following note:
R12: Recommended Browsers for Oracle E-Business Suite (Doc ID 389422.1)
Currently Firefox only opens the java plugin with 32-bit ESR version. The NAPI java plugin is not supported in Chrome.
If you patch and configure for the java web start, you can use Chrome or Edge.
Using Java Web Start with Oracle E-Business Suite (Doc ID 2188898.1)
Please try adding the following extension "Oracle E-Business Suite R12&11i Form Startup." in chrome and then try opening forms in chorme.