Yes. If you try to import a private key, it automatically detects whether or not it is actually a private key, and in case it doesn't recognize it as such, you won't be able to continue. It's most likely a copy and paste error from your side, or you decided to import multiple private keys in the wrong order. In case of the first option, make sure you select just the private key itself, and in case Electrum doesn't recognize it, there is a space either at the beginning or at the end of the private key. If you try to import multiple private keys, you should use this order;

5df6sdfsdf4sd5f4s4df5sdfs4g4fd4g5dfgdf45dfggf
54sdf4sd5sdfs55ds5f4s5df4f4sd5f4sd4fsd5f4f4dfs
57dsfsdf5sd54fs4dfs4df654sd5f4ds5f4dsf45f4d5s

And not;

sadasd4asd45asd4sadsad4sa5dsadsad4s4ds45a4

45asd45as4da4sf54sdf54sd5f4sd5f45ds64fsd4fs4

4654as54das54dasd45asd4a65s4d5a4sd5asd4d4d

Also not;

as5d64as65d4a5s4da4sas5d4s54d5s4d54asd54s5 54sad4asd4asd54s65a4ds5a4d54asd654asd5da sa5d45s4ds5a4da5s4d54as54sa45das54d