What does "card" and "make up" here mean?

What does "card" and "make up" here mean?

{}It was heralded by a notice from Dale Owen, dated January 5, to the effect that evidence had been laid before him which compelled him to withdraw his previous expressions of confidence in the Holmeses. A similar card was issued by Dr. Child. Writing to Olcott, who after his Eddy investigation was recognized as an authority, Dale Owen said: "I believe they have been latterly playing us false, which may be only supplementing the genuine with the spurious, but it does cast a doubt on last summer's manifestations, so that I shall probably not use them in my next book on Spiritualism. It is a loss, but you and Mr. Crookes have amply made it up."

https://www.macmillandictionary.com/dictionary/british/make-up_1#make-up_1__5

"Card" I would guess reflects the same meaning as "notice" in the previous sentence.

"Made it up", in the above, appears to mean that those two individuals have made contributions which compensate for the losses due to "they" (whoever they are) "playing us false" (ie, fabricating claims).