Reposted from: https://wordpress.org/support/topic/failure-to-import-and-invalid-post-type-errors
UPDATE: WORKAROUND FOR FAILED TO IMPORT
Anyone having the issue where author’s are NOT being recognized or the XML import data is failing…
I am not certain if this is something missing on the certain servers or if it’s the plugin itself is buggy as this it works for me on some server and not others using identical environments.
If your import is failing try the following (this method resolved this issue for me):
1) Download and Install 7zip.
2) Right click on your .XML file -> 7zip -> Add to Archive
3) Change the “Archive format” to gzip and hit “OK”
4) Try to import the file again (using the .gz you just created) and it should work.
NOTE: May have to do the below. I didn’t.
I also had to bump up the following settings in my php.ini (these settings might be a bit excessive but my importer step 2 was going to a “page not found” front end error until I did this):
memory_limit = 64M
default_socket_timeout = 600
pfpro.defaulttimeout = 600