how did you get it to your server?  via ftp or the wp plugin installer?

have you tried again since the upload may have been corrupted?

I used the WordPress uploader and also got the error

I deleted the simple press folder and reinstalled using the uploader and again got the error

I deleted the simple press folder again,unzipped simple-press on my PC and uploaded via Filezilla

First try failed as I uploaded the top simple-press directory without noticing that when it unzipped there was a second simple-press directory downloads/simple-press/simple-press

I uploaded the correct simple press directory into wpcontent/plugins and this time it showed up on my Plugin List and I was able to successfully activate

whoo hoo!

Glad to hear you got it installed but we don’t hear about many issues. It used to be that FileZilla would almost always corrupt any zip file over 2mb bit we do not see that often these days. Certainly the majority instilling the core plugin seem to have no problem. Sorry to hear you did.

I just did the same thing…  Installed OK and went to activate it….  Error came back and said. “The plugin does not have a valid header.”

I used the wordpress plugin installer directly after install.

THEN 

I went to the list of installed plugins and I clicked on the activate from there.  And it gave me this message:

Plugin could not be activated because it triggered a fatal error.
Fatal error: Cannot redeclare sp_get_option() (previously declared in /home/content/a2pewpnaspod04_data03/20/41200220/html/wp-content/plugins/the-events-calendar/src/functions/template-tags/deprecated.php:500) in /home/content/a2pewpnaspod04_data03/20/41200220/html/wp-content/plugins/simple-press/sp-api/sp-api-primitives.php on line 81

looks like you have another plugin Events Calendar that has named a function exactly the same as ours…  thought they had actually changed that in the latest version, but perhaps I am thinking of something else…  though it appears to be in a deprecated function file…

not much we can do there…  you will have to change all occurrences within one… or perhaps just try deleting it from that deprecated function if you dont have any event calendar add ons still using a deprecated function…