When you updated the ACF, you should see a notice that asks you to upgrade the database. I’ve attached a screenshot for your reference. If you don’t see it, then your database is not upgraded yet.
If you have a backup of your site before updating ACF, I suggest you restore it and then deactivate the other plugins you have and change your theme to WordPress’ stock theme (such as Twenty Sixteen).
Also, I suggest you increase the PHP maximum execution time in case you have a lot of data in your database. This page should give you more idea about it: http://stackoverflow.com/questions/5164930/fatal-error-maximum-execution-time-of-30-seconds-exceeded.
After that, kindly try to update ACF again and then upgrade the database when requested.
If the issue persists, could you please open a new ticket and provide temporary admin credentials to your site? You can open a new ticket here: https://support.advancedcustomfields.com/new-ticket. Also, please don’t forget to explain the issue again and provide the link to this thread.
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