If you get the error 'Too Many Activation Attempts' when you try and apply a Steam key then you will need to wait for a few hours before you try and add the remainder of the keys.
Steam has a limit which stops more than about 20 keys being added in a short space of time, the limit may be lower if you enter invalid keys.
Fanatical.com can't help you get your keys added any quicker, the limit is imposed by Steam.
https://support.steampowered.com/kb_article.php?p_faqid=276 has some more useful information about this error.
If Steam reports "Too Many Activation Attempts" either:
- Come back to activate the additional games later.
- Log into Steam using a different account to activate the other games