I cannot use certain tools in my Illustrator, for example, line, scissor. etc.
Can somebody tell me what's going on?
What do you mean exactly when you say you can't use them? Do the shortcuts work (\ for line tool, C for scissors)?
I cannot click on it, and shortcuts don't work as well. I am completely new to Adobe but downloaded the Cloud, paid for it just a couple of days ago and this is my first-day using Illustrator, and when I wanted to use the line tool then I realized that it's not working also with a bunch of others.
You did not click on the 3 dots in the tool panel, no?
Just go to Window > Tools > Advanced should help.
Thanks Monika, exactly this I needed, Advanced panel. It is my first day with Illustrator:)
This could sound like a preference corruption.
You can try the (relevant parts of the) LIST, irrelevant parts omitted.
Sometimes, (certain) things may fail or stop working for no apparent reason. When the (other) possible reasons/cures fail to work, it may be some kind of (temporay or permanent) corruption, or even some inconvenient preference setting(s), which may be cured with something on the following list set up in an attempt to provide a catchall solution for otherwise unsolvable cases. It starts with a few easy and harmless suggestions 1) - 3) for milder cases, and goes on with three alternative ways 4) - 6) of resetting preferences to the defaults (easily but irreversibly and more laboriously but more thoroughly and also reversibly), then follows a list 7) of various other possibilities, and it ends with a full reinstallation 8 ). If no other suggestions work, or if no other suggestions appear, you may start on the list and decide how far to go and/or which may be relevant.
You may have tried/done some of them already; 1) and 2) and 3) are the easy ones for temporary strangenesses, and 4) and 5) and 6) are specifically aimed at possibly corrupt/inconvenient preferences); 7) is a list in itself, and 8 ) is the last resort.
If possible/applicable, you should save current artwork first, of course.
1) Close down Illy and open again;
2) Restart the computer (you may do that up to at least 5 times);
3) Log out of your Adobe account and log back in;
4) Close down Illy and press Ctrl+Alt+Shift/Cmd+Option+Shift during startup (easy but irreversible);
6) Follow the instructions here: https://helpx.adobe.com/illustrator/using/setting-preferences.html
Even more seriously (this may be serious because you may need to restore plugins and whatnot afterwards if you have customized things), you may:
8 ) A) Uninstall (ticking the box to delete the preferences if applicable), B) run the Cleaner Tool (if you have CS3/CS4/CS5/CS6/CC), and C) reinstall. You may try without step B), but sometimes it is needed, because otherwise things may linger.
As it appears from this thread, it may be worth repeating this if it fails to help the first time:
Andrea, could you please tell us what platform you are on - Mac or PC- and what system. This would help to define the issues you are facing. Jacob's reply has many great suggestions but knowing the platform and the system would help!