No thumbnails with new install

I’ve just installed Document Gallery and tested the set up of a PDF gallery. The thumbnails are not being generated. There is nothing in the Thumbnail management, no errors in the log, and Ghostscript and Imagick are both installed. I am a somewhat beginner user so any help is appreciated.
Here is my test page:
http://www.theredguidetorecovery.com/7029-2/

Thank you!

Array
(
[thumber] => Array
(
[gs] => /usr/bin/gs
[active] => Array
(
[av] => 1
[gs] => 1
[imagick] => 1
[thumber-co] =>
)

[width] => 200
[height] => 200
)

[thumber-co] => Array
(
[uid] =>
[secret] =>
[subscription] => Array
(
)

[direct_upload] =>
[mime_types] => Array
(
)

)

[gallery] => Array
(
[attachment_pg] =>
[columns] => 4
[descriptions] =>
[fancy] => 1
[limit] => -1
[mime_types] => application,video,text,audio,image
[new_window] =>
[order] => ASC
[orderby] => menu_order
[paginate] => 1
[post_status] => any
[post_type] => attachment
[relation] => AND
[skip] => 0
)

[css] => Array
(
[text] =>
)

[meta] => Array
(
[version] => 4.3.1
[items_per_page] => 10
[donate_link] => https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=EE5LWRLG933EN&lc=US&item_name=Document%20Gallery%20Plugin&item_number=document%2dgallery¤cy_code=USD&bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted
)

[logging] => Array
(
[enabled] => 1
[purge_interval] => 7
)

)