Learn Italian: Siccome il ritratto era sfocato, non l'avevo stampato. - Since the portrait was blurry, I hadn't printed it.

Avevo stampato is the trapassato prossimo (past perfect). We use this tense to talk about an action that happened—or in this case, didn't happen—before another point or situation in the past. It translates perfectly to the English "had printed" rather than "have printed".

What is the l' attached to avevo?

It stands for lo (it), referring back to the masculine noun il ritratto. When the direct object pronouns lo or la come right before a form of avere that starts with an "a" or "h", they drop their vowel and become l'.

Would the ending of stampato change if we were talking about a photo (la foto) instead of a portrait?

Yes! When you use a direct object pronoun like lo or la with a compound tense, the past participle at the end must agree with the pronoun's gender and number. If it were a photo (feminine singular), the pronoun would be la (still shortened to l') and the participle would change to match: non l'avevo stampata.

Why does the sentence start with siccome instead of perché?