While I cannot prove this conclusively, for some time now, I have suspected that there may be times when Facebook will purposely restrict sharing and commenting on a wide scale; not because you have personally done anything wrong, but perhaps because their servers are being overloaded by their global audience of Facebook users. If this is true, it could be a part of Facebook’s “load balancing” mechanism, whereby they distribute the workload — such as web browser requests — across many of their servers. Technically, load balancing is defined as the methodical and efficient distribution of network or application traffic across multiple servers in a server farm. But even with that, if the load becomes too great, maybe Facebook simply prevents a certain region of the world from sharing or commenting for a short period of time until the load on their servers lightens a bit. But this is just a guess on my part.
At the same time, it could also be that Facebook has purposely restricted you personally, because you have been posting, commenting, sharing or tagging too fast. I discuss these issues in some of my other BBB Blog posts. Basically, if you surpass the hourly or daily quotas which they have set for a particular activity, they may in fact restrict you for hours, days, weeks or longer. Many Facebook users refer to this as being thrown in jail. Again, I have written a few blog posts about this issue as well. You may want to refer to the following links:
Why am I in Facebook Jail Theory:
https://www.billkochman.com/Blog/index.php/why-am-i-in-facebook-jail/
Locked Out of Facebook: Harassment or Error?:
https://www.billkochman.com/Blog/index.php/locked-out-of-facebook-harassment-or-error/
Does Facebook Really Persecute Christians?:
https://www.billkochman.com/Blog/index.php/does-facebook-really-persecute-christians/
There is a final reason regarding why you may not be able to share someone’s Facebook posts. This is fully explained in this BBB Blog post:
Warning Regarding Setting Facebook Privacy to ‘Friends’:
https://www.billkochman.com/Blog/index.php/warning-regarding-setting-facebook-privacy-to-friends/
I hope the above information has been useful to you.