I have the same issue. I got this error.
Opera installer 66.0.3515.44.0
Fatal error upon loading installer executable:
In line 201:The system cannot find the file specified. (0x2), In line 259:The operation completed successfully. (0x0), In line 290:The operation completed successfully. (0x0), In line 201:The system cannot find the file specified. (0x2), In line 259:The operation completed successfully. (0x0), In line 294:The operation completed successfully. (0x0), In line 180:The specified procedure could not be found. (0x7F),