Trying to Deactivate Google XML Sitemap plugin, get 500 internal error

Hi

So ive been getting this error in my debug log when trying to deactivate the Google XML sitemap?

[13-Feb-2019 17:48:00 UTC] PHP Warning: Unknown: open(/home/sites/autoprint.co.uk/tmp//sess_4t8frm6ae4pi54cl3dnlogg6n4, O_RDWR) failed: No such file or directory (2) in Unknown on line 0
[13-Feb-2019 17:48:00 UTC] PHP Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/home/sites/autoprint.co.uk/tmp/) in Unknown on line 0

I’ve seen this same error before with other stuff on my site so i am starting to think this is related to my hosting or something I have set up incorrectly in my .htaccess or php settings? But my hosting provider is a one man band who never gets back to us, pretty terrible host provider tbf but i dont make the decision when it comes to our host, so i thought I would try to settle this myself before going to my hosting provider as I know he will take ages or give me very little support.

Im lost Ive looked online to find nothing related to the above error message and WordPress. A moderator for the WordPress plugin forum said WordPress doesnt even use sessions. So what could this be? This is really doing my head in, Its the one thing thats stopping me from wanting to take my site live, first impressions mean a lot and i dont want a ton of errors popping up for our visitors.

Hope someone can help

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